个人网上银行动态口令卡每张卡片覆盖有（）个不同的密码。
A.10
B.20
C.30
D.40
参考答案：C
He broke his leg last week. The doctor asked him ________ in bed for two weeks. [ ]
A. to stay
B. stayed
C. staying
D. stays
有机固体废物的好氧堆制可人为的划分为几个时期？都有哪些微生物参与？
