具有趋化作用的是()
A.C5a
B.C1q
C.C3
D.I因子
E.H因子
参考答案:A
Kate's handwriting(书法) is better than _____ in the class. [ ]
A. anyone else
B. anyone's
C. any other else
D. anyone else's
简述步进梁的工作原理。