This is the first time astronomers ____the whole process of a black hole ___a star, from its first
问题描述：
This is the first time astronomers ____the whole process of a black hole ___a star, from its first
to nearly final bites.
A see eat B have seen eatingC saweatenD had seeneat
这个句式是不是用完成时呢?
答
是用现在完成时
It/This is the first/second/……/last time that +现在完成时
It/This was the first/second/……/last time that +过去完成时