弗洛伊德认为心理发展的动力来自于（）
A.遗传
B.环境
C.性本能
D.超我
E.学习
参考答案：C
液碱中氢氧化钠浓度为（）
A、3%
B、30%
C、60%
Bob________after his classmate in the classroom when his teacher________.[ ]
A. ran;turned up
B. was running;turned up
C. was running;would turn up
D. had run;would turn up
