．—That must have been a long trip.

—Yeah, it________us a whole week to get there.

A．takes

B．has taken

C．took

D．was taking

达到形态成熟的种子具有的特点是：（）。

A．呼吸作用强

B．含水量高

C．种皮坚硬、致密，抗旱力强

D．种子不饱满