— Shall I give you a ride as you live so far away?

— Thank you, ________. [ ]

A. it couldn't be better  

B. of course you can

C. if you like  

D. it's up to you

甲与乙为夫妻，甲因有婚外情，欲毒死乙，便从村小卖部买来两包老鼠药投入乙的饭碗中，但因老鼠药存放时间过久而失效，乙并未被毒死，甲的行为构成（）。

A.犯罪预备

B.犯罪中止

C.犯罪未遂

D.犯罪既遂