______ cheese do you want?
A:How many
B:How much
C:how many
D:how much
已知曲线x=2pt2y=2pt(t为参数,p为正常数)上的两点M,N对应的参数分别为t1和t2,且t1+t2=0,那么|MN|=____ .
下列属于生命现象的是( )