在血液中具有释放促进血液凝固的物质、促进止血作用的成分是[ ]
A．红细胞
B．血小板
C．白细胞
D．血浆
答案：B
若2n=a，5n=b，20n=c，则c=______（用a，b表示）．
________, I think, and the problem could be settled．
A．A bit more effort
B．So long as you keep up your spirits
C．If you doubt your efforts
D．Making great efforts
