目前应用最为广泛的生物安全柜柜型为()。
A.一级生物安全柜
B.二级生物安全柜
C.三级生物安全柜
D.四级生物安全柜
E.以上都是
参考答案:B
Although he has failed many times, he keeps _____ hard to make his dream come true.
A. working
B. to work
C. worked
量度物体惯性大小的物理量是______,在国际单位制中,它的基本单位是______.