The best time ___ is in autumn. [ ]
A.travelling
B.to travel
C.travels
D.traveled
答案:B
Don't ______. I'll help you.[ ]
A. worry
B. worried
C. be worry
D. to worry
常用于凝血项检查和血液保养液中的抗凝剂是()
A.EDTA
B.草酸钠
C.枸橼酸钠
D.双草酸盐
E.肝素