问题，高手帮忙

hardball

while play is important at all levels of human developments. _____takes on particular signifcance when children are 5 and 6 years old.

A it

B and

C which

D because it

正确的是it  A

我选的B,为什莫错？我理解是一个句子两个谓语?

enjoylife517

因为整个句子开头有while这个连接词，所以如果用其他的，就缺少主句了，所以必须补出主语it。