与CDK4和CDK6的抑制密切相关的CKIs是（）
A.cdc2
B.p53
C.p21
D.p16
E.cyclinD
参考答案：D
If you work hard at your English, I'm sure you will ____ speak English very well next year. [ ]
A. can
B. able to
C. be able to
D. be able
2100年是闰年。[ ]
