C. To try                          D. To have tried

以下各题也应选A，是因为句中的从属连词 when, before, until 等（填空句为祈使句）：

(8) ______ him enough time to get home before you telephone.

A. Give                             B. To give

C. Giving                          D. Given

(9) ______ left when you get to the end of the street.

A. Keep                            B. Keeping

C. To keep                       D. Kept

(10) ______ your hand over your mouth when you cough.

A. Put                              B. Putting

C. To put                         D. To be putting

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