A:twice as much protei
B:protein as much twice
C:twice protein as much
D:protein as twice much
如图,直线AB⊥平面BCD,∠BCD=90°,则图中直角三角形的个数为____.
关于胚胎发育及胚胎工程的叙述正确的是( )
_________ does he want to join our club?
对于一个已经带电的物体,下列说法中正确的是 ( )