阅读下列短文,从每题所给的 A、B、C、D 四个选项中选出最佳答案。
A
A news agency has recently collected ideas from scientists of what aliens could really look like. Many scientists believe that their appearances have very close relationship with the natural environment. Let's check out their alien ideas.

Insects with wide wings
For worlds with a low-density atmosphere（低密度大气）, life forms may have huge wings to fly.
Crab-like creatures
Scientists imagine that there might be sea creatures such as crabs（螃蟹） in underground oceans.

Tiny creatures
It is possible that there are simple single-celled(单细胞的) creatures that can't be seen by human eyes.
Short and strong aliens
Creatures on a planet which is heavier and has stronger gravity than the earth may be shorter and stronger than humans.
Animals with long legs
On a planet smaller than the earth, there may be tall aliens because of the force of weaker gravity.
Human-like aliens
Creatures can look similar to humans if they live in conditions like the earth, both in terms of gravity, atmosphere and temperature.
() 1. Aliens may be shorter and stronger than humans because of the .
A. low atmosphere B. heavier gravity
C. condition like the earth D. different temperatures
() 2. According to the text, tall aliens may .
A. live on a smaller planet B. look similar to humans
C. be much taller than humans D. also have long arms
() 3. Which of the following can be the best title for the text?
A. Creatures in the world B. Humans in the future
C. Aliens in scientists' minds D. Sea animals in the ocean