一个DNA经过4次复制,形成16个DNA分子,其中含最初DNA链的DNA分子有[ ]
A.2个
B.4个
C.8个
D.16个
答案:A
The music he is playing sounds_____.
A.nicely
B.sweetly
C.lively
D.pleasantly
拼装夹具具有()的优点。
A.专用夹具
B.可调夹具
C.成组夹具
D.组合夹具