问题
选择题
— I don't know_ .
— You can go and ask Jack.
A．when does the train leave
B．that we will plant trees or not
C．if she had come yesterday
D．what I should buy for him
答案
答案：D
宾语从句语序的用法。I don't know后为宾语从句，要用陈述语序，故A错，C应该为过去时，不是过去完成时，由答语知道是给Jack买东西的，D又是陈述语序，故选择D。