47．What do you have to do when sailing against the wind? 　　(A)Move in a straight line. (B)Allow the sail to flap. 　　(C)Lower the sail. (D)Tack the boat.

51．What should we do before attempting to “read” people? 　　(A)Learn about their relations with others. 　　(B)Understand their cultural backgrounds. 　　(C)Find out about their past experience. 　　(D)Figure out what they will do next.