请教新东方教材上问题

P92第5题：A recent study of ancient clay deposits has provided new evidence supporting the theory of global forest fires ignited by a meteorite impact that contributed to the extinction of the dinosaurs and many other creatures some 65 million years ago.

(A) 如上划线

(B) 将A中最后的that 去掉

答案选了B，但我觉得后面的contributed 这个动词是impact 主动发出的，如果去掉that 不是成了过去分词的省略结构了吗，不知我的理解对否

P95第14题：答案选项中A newly developed jumbo rocket will be able to deliver a heavier load of instruments into orbit than the space shuttle can, and at a lower cost.——than 前后分别是be able to 和can，能这样对称吗？

请nn指教~

contribute是theory of global forest fires发出的，因为去掉ignited by a ..impact句子也成立。如果按照你那样的理解，是由impact发出，也就是如果选a的话，我觉得contribute的时态就应该和主句一样用一般现在时。