Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
Planet of No-Return By WILBUR S. PEACOCK The orders were explicit: "Destroy the 'THING' of Venus." But Patrolmen Kerry Blane and Splinter Wood, their space-ship wrecked, could not follow orders—their weapons were useless on the Water-world. on an exploration trip this important—well, I'll never understand." were changing your pants twenty times a day. When I want advice on how to fly a ship, how to cure space bends, how to handle a Zelta ray, or "All right, all right!" Splinter tucked the capsule box back into his pocket, grinned mockingly. "But don't say I didn't warn you. With this shielded ship, and with no sunlight reaching Venus' surface, you're gonna be begging for some of my vitamin, super-concentrated pills before we get back to Earth." passing years, he had flight-tested almost every new experimental ship, had flown them with increasing skill, had earned a reputation as a a rusty old freighter couched between the gleaming bodies of great space warriors. Interplanetary Squadron because of his inherent skill, even though his formal education had been fairly well neglected. Now, the two of them rode the pounding jets of a DX cruiser, bound for Venus to make a personal survey of its floating islands for the Interplanetary Squadron's Medical Division. "Ten to one we don't get back!" Splinter said pessimistically. the warmth of their friendship was a tangible thing in the small control-room of the cruiser. Venus. Excitement lifted their spirits, brought light to their eyes as they peered eagerly ahead. "What's it really like?" Splinter asked impatiently. Venus is a tricky place to set a ship on." He yawned again, drifted instantly into sleep, relaxing with the down at his sleeping partner, then turned back to the quartzite port. He shook his head a bit, remembering the stories he had heard about the water planet, wondering—wondering— II Venus was a fluffy cotton ball hanging motionless in bottomless space. Far to the left, Mercury gleamed like a polished diamond in the sunlight. Kerry Blane cut the driving rockets, let the cruiser eager and reckless, his eyes seeking to pierce the clouds that roiled and twisted uneasily over the surface of the planet. Kerry Blane glanced tolerantly at his young companion, felt a nostalgic tug at his heart when he remembered the first time he had approached the water-planet years before. Then, he had been a young and reckless firebrand, his fame already spreading, an unquenchable fire of brought the patrol cruiser closer to the cloud-banks on the line of demarcation between the sunward and sunless sides of the planet. He hummed tunelessly, strangely happy, as he peered ahead. destroy the thing that killed him." after all, it's just an The great cottony batts of roiling clouds rushed up to meet the ship, bringing the first sense of violent movement in more than a week of flying. There was something awesome and breath-taking in the speed with which the ship dropped toward the planet. Tendrils of vapor touched the ports, were whipped aside, then were through sheer instinctive ability, seeming to fly it as though he were an integral part of the ship. and still the clouds pressed with a visible strength against the ports. The rockets drummed steadily, holding the ship aloft, dropping it slowly toward the planet below. Then the clouds thinned, and, incredibly, were permeated with a dim and glowing light. A second tossed in a majestic display of ruthless strength an ocean that seemed to be composed of liquid fluorescence. His voice stilled, and he was silent, his eyes drinking in the weird incredible scene below. The ocean was a shifting, white-capped wash of silvery light that gleamed with a bright phosphorescence of a hundred, intermingled, kaleidoscopic colors. And the unreal, unearthly light continued more bright than moonlight. Splinter turned a wondering face. "But the official reports say that there is no light on Venus," he exclaimed. "That was one of the reasons given when exploration was forbidden!" Kerry Blane nodded. "That was merely a pretext to keep foolhardy spacemen from losing their lives on the planet. In reality, the ocean is alive with an incredibly tiny marine worm that glows phosphorescently. The light generated from those billions of worms is reflected back from the clouds, makes Venus eternally lighted." He turned the ship to the North, relaxed a bit on the air bunk. He felt tired and worn, his body aching from the space bends of a few hours before. "Take over," he said wearily. "Take the ship North, and watch for any throat, and he tapped his companion's arm. "Take a look!" he called excitedly. They fought in the ocean below, fought in a never-ending splashing of what seemed to be liquid fire. It was like watching a tri-dim screen of a news event, except for the utter lack of sound. in the phosphorescent water like beings from a nightmare, exploding out of their element time and again, only to fall back in a gargantuan jaws agape, wrenched and ripped at the smooth black throat of the other creature. The second creature rippled and undulated in agony, whipping the ocean to foam, then went limp. The victorious monster circled the body of its dead foe, then, majestically, plunged from sight into the ocean's depths. An instant later, the water frothed, as hundreds of lesser marine monsters attacked and fed on the floating corpse. "Brrrr!" Splinter shivered in sudden horror. Kerry Blane chuckled dryly. "Feel like going for a swim?" he asked black on the horizon. Glowing water flashed beneath the ship, seeming to smooth into a gleaming mirror shot with dancing colors. There was no sign of life anywhere. Thirty minutes later, Kerry Blane circled the island that floated free in the phosphorescent ocean. His keen eyes searched the tangled luxuriant growth of the jungle below, searching for some indication that the protoplasmic monster he seeked was there. understand it, anyway, this chunk of animated appetite hangs around an island shaped like a turtle. However, our orders are to investigate every island, just in case there might be more than one of the monsters." exploring of the other islands." He swung the cruiser in a wide arc to the north, trebling the flying speed within minutes, handling the controls with a familiar dexterity. He said nothing, searched the gleaming ocean for the smudge of blackness that would denote another island. His gaze flicked amusedly, into a comfortable position, dozed sleepily. Kerry Blane rode the controls for the next three hours, searching the limitless ocean for the few specks of islands that followed the slow currents of the water planet. Always, there was the same misty light surrounding the ship, never dimming, giving a sense of unreality to the scene below. Nowhere was there the slightest sign of life until, in the He peered through the port, seeking any spot clear enough for a landing field. Except for a strip of open beach, the island was a solid mass of the next, clamber through the port. They stood for a moment in silent wonder, staring at the long lazy rollers of milky fluorescence that rolled endlessly toward the beach, then turned to gaze at the great fern-like the growths on the water world. Kerry Blane walked the length of the cruiser, examining the slight damage done by the crash, evaluating the situation with a practiced about, and head her toward the sea." you didn't think of it and I most certainly forgot! Solar rays can't penetrate the miles of clouds on Venus. Those guns are utterly useless as weapons!"

<question>:
What is the main goal of their trip to Venus?

<options>:
A To find the turtle that lives in Venus's ocean
B To bring home samples of the glowing marine worms
C To exterminate a particular protoplasm that killed another human
D To observe the interactions between the sea creatures on Venus

<answer>:

C