维持细胞较快的生长增殖速度,需添加的血清量为()
A.1%~2%
B.2%~5%
C.5%~10%
D.10%~20%
E.20%~25%
参考答案:D
The traffic problems have severely affected economic development. ________, we must spare no efforts to solve them.
A.Furthermore
B.Therefore
C.Meanwhile
D.Nevertheless
国家机器的形成,是警察产生的政治条件。( )