下列材料用以证明案件事实时属于书证范畴的有：A．只有一方当事人签名的合同文书 B．刻

胎儿窘迫的早期表现是（）

A.胎动消失

B.胎动减弱

C.胎动频繁

D.胎动增强

E.胎动次数减少

There____________ many trees in front of my house now.

A．is

B．are

C．was

D．Were

.The Chinese language differs from many Western languages___________it uses characters which have meanings and can stand alone as words.

A．unless

B．until

C．now that

D．in that

在诗歌、俗语及成语中经常包含着一些科学原理，请你用化学方程式表示下列相应的化学原理

A：______；B：______．