［典型考例 1 ］ In the dark street there wasn't a single person_____ she could turn for help. A. that B. who C.from whom D.to whom
析：答案为 D 。介词 to 和定语从句中的 turn 构成固定搭配 turn to sb. for help。 意为“向某人求助”。
2 ．根据定语从句意思的需要，此时不但要注意其前的搭配也要注意其后的搭配。
如：• He had a bad cold， because of which he didn't attend the meeting.
他患了重感冒，因此未能参加会议。
• The speed at which the car runs depends on the road condition. 这辆车的速度要根据路面状况而定。
