This is the third time we      a film in the cinema together as a family.

A．see

B．had seen

C．saw

D．have seen

幼苗子叶留土的主要原因是种子萌发时哪一部份几乎不伸长（）

A.上胚轴

B.下胚轴

C.胚根

D.胚芽