下列符号中，能表示一个氮分子的是A．NOB．2NC．2N2D．N2
---Miss Smith, can I go home after I finish my homework? ---No, you ______ stay here until I come back. A. can B. may C.
It is important ______ the piano well. A.of him to play B.for him to play C.of him playing D.for him playing
如图是某生物有丝分裂过程中核DNA含量变化曲线图，下列关于曲线各段的描述正确的是 ( ) A.若E表示的是分裂末期，则f段的DNA含量和cd段的相
下列各句中，加点的成语使用恰当的一项是 A．软件的开发和制作，是计算机领域的重要工程。小到一个课件，大到一个数据库，都不是一件一蹴而就
．下列事故的处理方法中，不正确的是（ ） A．正在使用的电器着火，立即用水浇灭 B．燃着的酒精灯不慎碰倒，立即用湿布盖灭 C．炒菜时油锅中的油
The missing children haven’t been found yet. Something terrible ________ to them. A. may happen B. should have happened C. must happen D. might have happened
.Fifty-two miners were killed in the accident. ______ , thirty-six were missing. A . In addition B. On the other hand C. On this occasion D. In brief
=sin2θ+4cos2θ. 
