下列描述中，正确的一条是______。A．关系表达式的值是一个逻辑值，即“真”或“假

用恰当的词语填空．完成对话。每空一词。(每小题1分．共5分)

W: Excuse me, is there a bookstore around here?

M: Yes. There is 小题1:        on Zhongshan Road. It's between the parking lot and the supermarket.

W: How 小题2:         is it from here?

M: About thirty minutes' walk. You can 小题3:        the No. 14 bus there.

W: Thank you. By the way,小题4:          the bus stop?

M: It's at the end of this street. You can't 小题5:          it.

W: Thanks for your help.

M: You're welcome.

下列应用不正确的是--------------------------------------------------------(    )

A．二氧化碳作气体肥料

B．氧气用于气焊

C．熟石灰改良酸性土壤

D．食盐配制生理盐水

能从数据信号波形中提取同步信号的典型编码是（）

A.归零码

B.不归零码

C.定比码

D.曼彻斯特编码

锅炉用钢管应具有良好的热力加式工艺性，特别是（）性要好。

A.可锻

B.可焊

C.铸造

D.切削加工

小儿多大年龄时巴彬斯基征应为阴性

A．6个月

B．1岁

C．1.5岁

D．2岁

E．2.5岁