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

<passage>:
By CARL JACOBI Grannie Annie, who wrote science fiction under the nom de plume of Annabella C. Flowers, had stumbled onto a murderous plot more hair-raising than any she had ever concocted. Planet Stories Fall 1944. Extensive research did not uncover any evidence that I was killing an hour in the billiard room of the Spacemen's Club in Swamp City when the Venusian bellboy came and tapped me on the shoulder. Grannie Annie! I barged across the lounge and seized her hand. "Grannie Annie! I "Hi, Billy-boy," she greeted calmly. "Will you please tell this and Grannie Annie her usual whisky sour—I waited until she had tossed the drink off at a gulp before I set off a chain of questions: "What the devil are you doing on Venus? Don't you know women aren't allowed in the Spacemen's "Hold it, Billy-boy." Laughingly she threw up both hands. "Sure, I knew they are. Anyway, I've been thrown out of better places." She hadn't changed. To her publishers and her readers she might be Annabella C. Flowers, author of a long list of science fiction novels. But to me she was still Grannie Annie, as old-fashioned as last year's sat back and massaged their digits, watching their earnings mount. One thing you had to admit about her books. They may have been dime novels, but they weren't synthetic. If Annabella C. Flowers wrote a novel, and the locale was the desert of Mars, she packed her carpet bag and hopped a liner for Craterville. If she cooked up a feud between two "What happened to Guns for Ganymede ?" I asked. "That was the title of "It wasn't Guns , it was and it wasn't Ganymede , it was Pluto ." I grinned. "All complete, I'll bet, with threats against the universe the jetty front. Grannie Annie hailed a hydrocar. Five minutes later we THE QUESTION PROGRAM OF THE SYSTEM As we strode down the aisle a mangy-looking Venusian began to pound a tinpan piano in the pit. Grannie Annie pushed me into a seat in the yet." The piano struck a chord in G, and the curtain went rattling up. On the stage four Earthmen, two Martians, two Venusians, and one Mercurian sat on an upraised dais. That is to say, eight of them sat. The Mercurian, a huge lump of granite-like flesh, sprawled there, palpably myself. I am Doctor Universe, and these are my nine experts." There was a roar of applause from the Satellite sets all over these planets listeners will appear and voice questions. These questions, my nine experts will endeavor to answer. For every question missed, the sender will receive a check for one thousand planetoles . her wits with the experts. May I present that renowned writer of science fiction, Annabella C. Flowers." From the left wing Grannie Annie appeared. She bowed and took her place voice echoed through the theater: " Who was the first Earthman to titter the sunward side of Mercury? " Doctor Universe nodded and turned to Grannie Annie who had raised her tracto-car." And so it went. Questions from Mars, from Earth, from Saturn flowed in the visi sets. Isolated miners on Jupiter, dancers in swank Plutonian cafes strove to stump the experts. With Doctor Universe offering bantering side play, the experts gave their answers. When they failed, It grew a little tiresome after a while and I wondered why Grannie had general surveying his army. His black eyes gleamed, and his thin lips Grannie Annie came out from behind the box office then. She took my arm "Billy-boy, did you see the way that crowd acted?" she began. "When it was finished I had planned to take a six months' vacation, but those fool publishers of mine insisted I do a sequel. Well, I'd used Mars and Pluto and Ganymede as settings for novels, so for this one I decided on Venus. I went to Venus City, and I spent six weeks in-country. I got some swell background material, and I met Ezra Karn...." I was sitting up now, hanging on to the woman's every word. "Now in 2710, as you'd know if you studied your history, the three planets of Earth, Venus, and Mars were under governmental bondage. The cruel dictatorship of Vennox I was short-lived, but it lasted long enough to endanger all civilized life. ordered must be kept in each household. The effect on the people was followed." Grannie Annie lit a cigarette and flipped the match to the floor. "To go back to my first trip to Venus. As I said, I met Ezra Karn, an old prospector there in the marsh. Karn told me that on one of his travels into the Varsoom district he had come upon the wreckage of If Grannie expected me to show surprise at that, she was disappointed. police officials murdered on Pluto and a demand that government by representation be abolished on Jupiter. The time is ripe for a military dictator to step in. "And you can lay it all to the Green Flames. It seems incredible that a en masse ." appeared. On the booth wall a scant inch above Grannie's head the Grannie Annie leaped to her feet, grasped my arm and raced for the ganet , the tough little two headed pack animal of the Venus hinterland. Any form of plane or rocket would have had its motor instantly destroyed, of course, by the magnetic force belt that encircled the planet's equator. Now our drivers changed to It was around the camp fire that night that Grannie took me into her isolated crime there. But viewed from the perspective Grannie had undulating sweeps toward the center of the camp. Fascinated, I watched appeared. Grannie gave a single warning: Grannie Annie fired with deliberate speed. tent and faced me with earnest eyes. "Billy-boy, our every move is the swamp had undergone a chemical change and evolved into a cohesive multi-celled marine life that lived and died within a space of hours. The Venusians paddled with extreme care. Had one of them dipped his hand into one of those yellow streaks, he would have been devoured in a matter of seconds. dressed in varpa cloth, the Venus equivalent of buckskin, and on his head was an enormous flop-brimmed hat. Grannie Annie came to the point abruptly. When she had explained the "What do you mean?" Grannie paused in the act of rolling herself a Venusians. And then as we were about to leave, Karn suddenly turned. "The Doctor Universe program," he said. "I ain't missed one in months. You gotta wait 'til I hear it." Grannie frowned in annoyance, but the prospector was adamant. He screen, a curious numbing drowsiness seemed to steal over me and lead my thoughts far away. Half an hour later we headed into the unknown. The Venusian boatmen were ill-at-ease now and jabbered among themselves constantly. We camped that night on a miserable little island where insects swarmed futility of the venture. Only the pleadings of Grannie Annie kept me Grannie gazed a long moment through binoculars. "Billy-boy, take three Venusians and head across the knoll," she ordered. "Ezra and I will circle in from the west. Fire a gun if you strike trouble." But we found no trouble. The scene before us lay steeped in silence. "Up we go, Billy-boy." Heat gun in readiness, Grannie Annie began to Grannie nodded. "Some kind of a broadcasting unit. The Green Flames in Suspended by insulators from the ceiling over them was a thick metal

<question>:
By what were Grannie Annie and Billy-boy being watched?

<options>:
A Ezra Karn, an old prospector
B Hunter-bird
C a drone
D By Venusians

<answer>:

B