任意两个整数的和是自然数的是（ ） A．必然发生的事件 B．确定事件 C．随机事

If you happen to see the process of cooking in a restaurant, you might see the cook using rubbish oil, which is a common _____ in China nowadays.

A．sense

B．rule

C．practice

D．activity

完成句子(共3小题, 每题3分, 满分9分)

根据相关要求准确补充完整以下句子；完全正确方可得分。

小题1: Rather than take a bus to go downtown, they preferred to go there on foot. (同义句转换)

ð They ________ __________ go downtown on foot ________ take a bus.

小题2:Although he did his utmost, he failed, which made him so upset about himself that he felt like crying. (同义句转换)

ð ____ ____ ____ all his efforts he failed, which made him so depressed that he felt like crying.

小题3: The librarian put the ______ (换回来的) books ______ _______ (放回原处).

焦虑障碍最常见的表现形式为（）

A.急性焦虑

B.惊恐发作

C.广泛性焦虑

D.社交焦虑障碍

E.金刚烷胺

下列有关细胞转化试验的描述错误的是（）

A.其不以致突变为观察终点，可以弥补以致突变试验来筛查化学致癌物的不足

B.试验的观察终点是恶性变的细胞

C.可检出非遗传毒性致癌物

D.可检出遗传毒性非致癌物

E.可应用于细胞转化试验的细胞有：原代细胞、细胞系和病毒感染细胞

人工流产时有关宫颈裂伤的说法不正确的是（）

A.宫颈过紧易发生

B.不按顺序进行宫颈扩张易发生

C.操作用力过猛易发生

D.妊娠月份过大易发生

E.发生率较高