引起疱疹性咽峡炎的病原体是（） A.呼吸道合胞病毒 B.腺病毒3、7型 C.副流感病

用所给词的适当形式填空。

1. They________ (come) to China two months ago.

2. Where________ (be) she last week?

3. The twins________  (be)  at school this morning.

4. ________ he________  ( tell)  you a story last Sunday?

5. We                ________  (not watch) TV last night.

在火灾自动报警系统中，感烟探测器按灵敏度分为三级，其中二级灵敏度探测器一般为( )。

A．绿色

B．黄色

C．红色

D．橙色

The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence, you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.

These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.

Although he played several musical instruments while being a child, Maestro Macintosh did not begin playing the piano until he was 23 years old.（）

A. while being a child

B. as a child

C. as in childhood

D. at the time of his childhood

E. at the time when he was a child

导致上述情况的医源性因素可能为

A．缩宫素应用不合理

B．分娩方式选择不当

C．解释安慰工作做得不够

D．观察不仔细

E．胎位判断错误

何时上环合适？