John told me that he had lost his key to the car, but he didn't really lose it-that's just a(an)________．[ ]

A．fool  

B．event

C．performance  

D．trick

型孔轮式排种器护种板的作用是：（），提高播种均匀性。

A.降低投种高度

B.存放种子

C.防止种子破碎

D.刮去型孔中多余种子