渗透压测定的原理是根据（）。
A.比重高低
B.黏度大小
C.冰点下降
D.沸点上升
E.溶解度上升
参考答案：C
______ some teenagers don’t realize is _______ difficult life can be after they get addicted to drugs．
A．What, how
B．That, how
C．What, what a
D．That, what
Good harvest this year has made it possible for us to supply walnuts ______ last year's prices.
A. at B. in C. against D. on
