It's time _____ supper now. [ ]
A. for have
B. have
C. to
D. for
答案：D
比较被试者内设计与被试者间设计的特点。
亲水性最强的是
A．乙醚
B．丙酮
C．苯
D．氯仿
E．乙酸乙酯
