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

<passage>:
The a scream. A huge reptilian head had materialized out of nowhere and was hanging in air, peering about uncertainly. A scaly green body followed, four feet away, complete with long razor talons, heavy hind legs, and a whiplash tail with a needle at the end. For a moment the creature floated upside down, legs tried to bury himself in his mother's coat collar. An indignant that. The energy factor," he mumbled. "Nobody thought of dimension—but the energy differential was the important one." "What about the energy?" side—a million of them unbalances four billion of us. All close range Pete could see that the "scales" were actually tiny wrinkles of satiny green fur. He knew, of course, that the Grdznth were mammals—"docile, peace-loving mammals," Tommy's PR-blasts had declared emphatically—but with one of them sitting about a foot away Pete had to fight down a wave of horror and revulsion. The creature was most incredibly ugly. Great yellow pouches hung down below flat reptilian eyes, and a double row of long curved teeth glittered sharply. In spite of himself Pete gripped green. "Like a rubber ball with a dent in the side. Push in one thought Earth was much nicer." "For them," whispered Tommy. side, the other side pops out. And we're the other side. "For them," Charlie said. always going east ?" "I'm afraid so, friend." "Oh, dear. I wanted Florida ." "Well, you seem to have drifted through into the wrong course. The climate is so much better, and they mustn't be disturbed, you know." "Of course," said Pete. "In their condition. I'd forgotten." "And I'm told that things have been somewhat unpleasant "Oh, not many, not many at all. Only the Wives—half a million or so—and their spouses, of course." The creature what sticking out his tongue at the Grdznth. The creature shifted uneasily. "Really, I think—perhaps Florida would be better." about a riot in Boston." He started to flip the switch, anybody, any time, at any price." "Please. Movies are getting Better by the Day." "Yes, I know. And the Grdznth are getting worse by the hour. They're coming through in battalions—a thousand a day! The more Grdznth come through, the more they act as though they own the place. Not nasty or anything—it's that infernal politeness that people hate most, I think. Can't get them mad, can't get them into a fight, but they do anything they please, and go anywhere they please, and if the people don't like it, the Grdznth just go right ahead anyway." Anybody who tries anything fancy gets thrown like a bolt of lightning hit him. Rumors are getting wild—people saying they can't be killed, that they're just moving in to stay." in their cultural background makes them stick strictly to their according to the math boys. It's a parallel universe, one scientists working with Charlie Karns. Most of the parallels are analogous, and we happen to be analogous to the Grdznth, a point we've omitted from our PR-blasts. They have an eight-planet system around a hot sun, and it's going to get lots hotter through parallel after parallel trying to find one they can cold and arid and full of impassable mountain chains. With an uphill fight they can make it support a fraction of their population." system for getting a good strong Grdznth population on the new parallel as fast as possible. The males were picked for brains, education, ability and adaptability chosen largely according to how pregnant they were." through, to rest and parturiate." looked narrowly at Tommy. "To be very blunt, what's the "It's the parallel universe business, of course," he said to According to our figuring, this must involve complete control of mass, space and dimension, all three. And time comes into one of the three—we aren't sure which." released the lid. Like a jack-in-the-box, two small white plastic spheres popped out and began chasing each other about in spin. "No wires?" "Four. There's a differential factor, and we can't spot it. them into constants that make sense. But we haven't cracked "And if you do, then what?" Charlie took a deep breath. "We'll have inter-dimensional which means the greatest advance in power utilization since fire was discovered. It might give us the opening to a "and how long the Grdznth gestation period will be." mass and dimension." cosmetician to the Public Relations men. "I say—I am advances Earth will have, the wealth, the power. No dice. The man on the street reads our PR-blasts, and then looks up to see one of the nasty things staring over his shoulder at the newspaper." "So you can't make them beautiful," said Pete. "Can't you make them cute?" "With those teeth? Those eyes? Ugh." "How about the 'jolly company' approach?" "Tried it. There's nothing jolly about them. They pop out of nowhere, anywhere. In church, in bedrooms, in rush-hour traffic through Lincoln Tunnel—look!" were snarled up for blocks on either side of the intersection. A squad of traffic cops were converging angrily on the center of the mess, where a stream of green reptilian figures seemed to be popping out of the street and lumbering through the jammed autos like General Sherman tanks. "Ulcers," said Tommy. "City traffic isn't enough of a mess as it is. And they don't do on for the office. "Things are getting to the breaking point. what is it now?" something." "Do something! You think I'm a magician? I can just make Heinz. I'm not the least interested in what is focused completely on a collection of five thousand letters, to penetrate? How much medium do you control?" One that will take your constituents by the ears." He looked at Tommy pityingly. "You've tried to make them lovable, but they aren't lovable. They aren't even passably attractive. There's one thing they are though, at least half of them." put together a PR-blast that will twang the people's heart-strings eagerly. "Maybe a few photographs—do you suppose maybe baby Grdznth are lovable?" "They probably look like salamanders," said Pete. "But tell the people anything you want. If we're going to get across the sanctity of Grdznth motherhood, my friend, anything goes." "It's genius," chortled Tommy. "Sheer genius." "If it sells," the senator added, dubiously. The planning revealed the mark of genius. Nothing sudden, harsh, or crude—but slowly, in a radio comment here or a newspaper story there, the emphasis began to shift from Determined movements to expel the Grdznth faltered, trembled with indecision. The Grdznth were ugly, they frightened little children, they were a trifle overbearing in their insufferable stubborn politeness—but in a civilized world you just stomach pains. "Why don't people respond "You want yesterday's rushes?" "What do you think I want? Any sign of a lag?" "Not a hint. Last night's panel drew like a magnet. The Analysis shook his head. "We could only make a guess with or it's the ax for Charlie." He chuckled to himself, and paced people begin seeing what the Grdznth are giving us, they'll welcome them with open arms." thing? We're out on a limb—way out. We're fighting for time—time for Charlie and his gang to crack the puzzle, time for the Grdznth girls to gestate. But what are we hearing from is what we're hearing through just as fast as they can. I'm beginning to wonder what are giving us." "Well, they can't gestate forever."

<question>:
Which of the following is the best theme for this story?

<options>:
A Aliens are dangerous
B Public Relations is manipulative
C Don't trust someone just because they're polite
D Ugly things are evil

<answer>:

C