下列细胞中具有成对染色体的是 [ ]

A．青蛙的受精卵

B．雄蛙排出的精子

C．雌蛙排出的卵细胞

D．乙肝病毒

--Alice, why didn't you come yesterday?

--I _________, but I had an unexpected visitor.

A．had

B．would

C．was going to

D．did