缓冲液pH值改变对电泳的影响主要表现为

A．偏离等电点越远蛋白质，带电愈多，电泳速度愈快

B．缓冲液pH越大所有蛋白质电泳速度越快

C．缓冲液pH值改变使介质两端电压改变

D．缓冲液pH越小所有蛋白质电泳速度越快

E．缓冲液pH值改变蛋白质的等电点

Friendship helps us understand ______ we are, ______ we need each other and ______ we can do for each other.

A. what
when
that
B. who
why
what
C. where
why
that
D. who
when
how much