天然来源的结构为右旋体，3个手性碳均为R构型（）
A.维生素B1
B.维生素D2
C.维生素K3
D.维生素C
E.维生素E
参考答案：E
— Sorry, Ann. I’m afraid that I can’t go to the magic show by David Copperfield with you.
—____. Who knows when he will be back here next time?
A．It doesn’t matter
B．Do as you like
C．What a shame
D．Take it easy
采集静脉血标本过程中应注意什么?
