密度计在颗粒分析试验中有哪两个作用?
参考答案:
一是测量悬液的密度,二是测量土粒沉降的距离。
—How does Bob usually go to work?
—He _______ take a bus, but now he is used to (习惯于) walking. [ ]
A. used
B. was used to
C. used to
D. is used to
飞越高大构架的高压线的高度,距高压线不得少于()。
A、20米
B、30米
C、40米
D、50米