You can learn more when you play _____ a great player in the tennis match.
句意：在网球比赛中，如果你和很棒的球员对打，你会学到更多东西。表示“（在比赛或战斗中）对（某人或某事物）；与……比赛；和……对抗”要用 against，故选选项D。
ー Why are you so happy?
— Because Peter invites me _____ on a trip to Mount Tai.
invite sb. to do sth. 意为“邀请某人做某事”，故答案为选项C。