1. 

Close-up images of Mars by the Mariner 9 probe indicated networks of valleys that looked like the stream beds on Earth. These images also implied that Mars once had an atmosphere that was thick enough to trap the sun's heat. If this were true, something happened to Mars billions of years ago that stripped away the planet's atmosphere.
This paragraph best supports the statement that
A. Mars now has little or no atmosphere.
B. Mars once had a thicker atmosphere than Earth does.
C. the Mariner 9 probe took the first pictures of Mars.
D. Mars is closer to the sun than Earth is.
E. Mars is more mountainous than Earth is.

Answer: Option A

Explanation:

The paragraph states that Mars once had a thick atmosphere, but that it was stripped away. The other choices, true or not, cannot be found in the passage.