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

<passage>:
One can't be too cautious about the people one meets in Tangier. They're all weirdies of one kind or another. Me? Oh, I'm A Stranger In native costume you'll see and Chinese, Hindus and Turks, Levantines and Filipinos, North Americans and South Americans, and, of course, even Europeans—from both sides of the Curtain. the world's poorest and some of the richest. The poorest will try to sell you anything from a shoeshine to their not very lily-white bodies, and the richest will avoid your eyes, afraid you might try to sell them something. In spite of recent changes, the As a result of them the permanent population includes smugglers and black-marketeers, fugitives from justice and international con men, espionage and counter-espionage agents, homosexuals, nymphomaniacs, alcoholics, drug addicts, displaced of every flavor. Local law limits the activities of few of and said, "Hello, Paul. the waiter. The tables were all crowded and since mine was a face he recognized, he assumed he was welcome to intrude. It was more or less standard procedure Paul said, "How are you, Paul was an easy-going, sallow-faced "Pogo and Albert are going to fight a duel," I told him, "and "Oh," I said, "the intellectual type." I scanned the front page. "The Russkies have put up another manned satellite." "They have, eh? How big?" "Several times bigger than Paul said, "What ever happened "What flying saucers?" both looked after her. "You know, what everybody was seeing a few years ago. It's too bad one of these bloody manned satellites wasn't up then. Maybe they would've seen one." "That's an idea," I said. way. I didn't know Paul very well, but, for that matter, it's comparatively seldom you ever get to know anybody very well played close to the chest. in the States. Just to say something, I said, "Where do you think they came from?" And when he looked Saucers." He grinned. "From Mars or Venus, or someplace." none of them ever crashed, or landed on the Yale football field , or something." Paul yawned and said, "That was always the trouble with those crackpot blokes' explanations of them. If they were aliens from space, then why not show themselves?" I ate one of the potato chips. It'd been cooked in rancid olive answers to that one. We could probably sit around here and think of two or three that made sense." Paul was mildly interested. "Like what?" "Well, hell, suppose for instance there's this big Galactic League of civilized planets. But it's restricted, see. You're not eligible for membership until you, well, say until you've developed space flight. Then you're invited into the club. Meanwhile, they send secret missions down from time to time to keep an eye on your progress." Paul grinned at me. "I see you in a neatly tailored gray jellaba, European style high-heeled shoes, and a pinkish silk veil so transparent that you after her. I said, "Or, here's another one. Suppose you have a very advanced civilization on, say, Mars." "Not Mars. No air, and too "Don't interrupt, please," I said with mock severity. "This is a very old civilization and as the planet began to lose its water and air, it withdrew underground. Uses hydroponics and so forth, husbands its water and air. Isn't that what we'd do, in a few million years, if Earth lost its water and air?" "I suppose so," he said. "Anyway, what about them?" "Well, they observe how man is going through a scientific boom, an industrial boom, a population boom. A boom, period. Any day now he's going to have practical space ships. Meanwhile, he's also got the H-Bomb and both sides of the Curtain, he's not against using it, if he could get away with it." Paul said, "I got it. So they're scared and are keeping an eye on us. That's an old one. I've read that a dozen times, dished up different." it's one possibility." "I got a better one. How's this. There's this alien life form that's way ahead of us. Their civilization is so old that they don't have any records of when it began and how it was in the things like wars and depressions and revolutions, and greed for power or any of these things giving us a bad time here on Earth. They're all like scholars, get it? And some of them are pretty jolly well taken by Earth, especially the way we are right now, with all the problems, get or how we're going to get there." where we're going ?" "Well, take half the countries in the world today. They're trying to industrialize, modernize, catch up with the advanced countries. Look at Egypt, and Israel, and India and China, and Yugoslavia and Brazil, and all the rest. Trying to drag themselves up to the level of the advanced countries, and all using different methods of doing it. But look at the so-called advanced countries. climbing crime and suicide rates, the loony-bins full of the balmy, unemployed, threat of war, spending all their money on armaments instead of things like schools. All the bloody mess of it. Why, a man from Mars would be fascinated, like." Paul said seriously, "You you always come up against this brick wall. Where are they, these observers, or scholars, or spies or whatever they are? Sooner or later we'd nab one of them. You know, Scotland Yard, or the F.B.I., or Russia's secret police, or the French Sûreté, or Interpol. This world is so deep in police, counter-espionage outfits and security agents that an alien would slip up in time, no matter how much he'd been trained. Sooner or later, he'd slip up, and they'd nab him." I shook my head. "Not necessarily. The first time I ever considered this possibility, it seemed to me that such an alien would base himself in London or New York. Somewhere where he could use the libraries for research, where anything goes. Nobody gives a damn about you or your affairs. For instance, I've known you a year or more now, and I haven't the slightest idea of how "That's right," Paul admitted. ask a man where's he's from. He can be British, a White Russian, a Basque or a Sikh and nobody could care less. Where are "No, you're not," he grinned. "I felt your mind probe back a few minutes ago when I was talking about Scotland Yard or the F.B.I. possibly flushing an alien. Telepathy is a sense not trained by the humanoids. If they had it, your job—and mine—would be considerably more difficult. Let's face it, in spite of these human bodies we're disguised in, neither of us is humanoid. Where are you really "What're you doing here on Earth?" I asked him. "Researching for one of our meat trusts. We're protein eaters. Humanoid flesh is considered quite a delicacy. How about you?" "Scouting the place for thrill tourists. My job is to go around to these backward cultures and help stir up inter-tribal, or international, conflicts—all according to how advanced they are. Then our tourists come in—well shielded, of course—and get their kicks watching it." Paul frowned. "That sort of practice could spoil an awful Amazing Stories December 1960. Extensive research did not uncover any evidence that the U.S.

<question>:
Why does Paul think an alien wouldn't be able to hide on Earth?

<options>:
A Aliens don't look like Earthlings.
B An alien would not be able to mimic a human enough to fit in with society.
C An alien wouldn't be able to assimilate into Earth's backward culture.
D The Earth has so many intelligence agencies, at least one would be watching when an alien gave itself away.

<answer>:

D