正确答案：CD
解析：
The idea is that many things can go wrong, because the launch is "...a great number...". Therefore, the launch is dependent on a great number of factors.
(B) does not quite work for a couple of reasons. First, the factors would be relevant to the launch, not vice versa. Besides that, it doesn't fully convey the meaning of "being based on," which is the meaning that makes the most sense: we want to say that the success of the launch is based on or affected by many factors, not just that it's related.
(A) and (E) create the opposite meaning.