Is there life on the other planets?

问题描述:

Is there life on the other planets?
Scientists agree there_____be,but that it would possibly be different from ours because different planets have different environment.A.could B.will C.shall D.had 为什么?

could-可以,表示可能,和后边的would不配套.
will-将,表示将来,不能肯定的事哪能用将来说?逻辑不符.
shall-应该,配would
had,没听说过有had be这种用法,had been、have to be还可能.