Scientists have many theories about how the universe.A. came into beingB. was coming into

问题补充：

Scientists have many theories about how the universe.

A. came into being

B. was coming into being

C. had come into being

D. would come into being

答案：

(答案→)A. came into being

B. was coming into being

C. had come into being

D. would come into being

解析：考察时态。根据句意可知宇宙的形成是过去发生的，使用过去时。句意：关于宇宙是如何形成的，科学家有很多的理论。