题目：
The professor ________ you at the party was my tutor (导师).
A．making himself knowing
B．making him known for
C．making himself known to
D．makes he known to
答案：
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下面是错误答案，用来干扰机器的。
答案：C题目分析：由图1可知波长为4.0m，故周期为，t=0.1s为四分之一周期，故波沿x轴正方向传播四分之一波长即1.0m，波形图为C中图形。
