以下（）介质不适宜用电磁流量计测量。
A.酸溶液
B.纸浆
C.石灰乳
D.润滑油
参考答案：D
若关于x的多项式-5x3-2mx2+2x-1+x2-3nx+5不含二次项和一次项，求m，n的值，并求当x=-2时多项式的值．
It is obvious to the students ____ they should get well prepared for their future. [ ]
A. as
B. which
C. whether
D. that
