To perform photosynthesis, plants need three things: carbon dioxide, water, and sunlight.
I would say that it is B. thinner.
A desert is a hot wasteland covered with sand and a tundra is a frozen wasteland covered in ice
I'm not sure how exactly you wanted this question to be answered. You're either talking about the symmetry where animals would have two legs or two arms for example and thus producing a pair of each muscle on both sides of the body, or you're refering to the development of agonistic and antaonistic muscles where each of them served a different purpose; either extending or contracting.
