烷化剂为（）
A.甲氨蝶呤
B.环己亚硝脲
C.长春新碱
D.阿霉素
E.6-巯基嘌呤
参考答案：B
— When did Prince William and Kate get married?
— They ______ for about two years.
A．have married
B．have been married
C．got married
D．have got married
胚胎冷冻方法有（）。
A.逐步降温法
B.一步细管法
C.玻璃化法
D.常温保存法
E.快速降温法
