在括号里填上适当的数。 13.4+6.35→（ ）-8.49→（ ） 28.7+

用括号中所给单词的适当形式完成下列句子.每空格限填一词。

1.This shop sells all kinds of __________ from different countries. (watch)

2.Students should be taught how to learn by __________. (they)

3.We were told to turn right at the __________ traffic light. (three)

4.It's natural for us to become more __________ when we get old. (forget)

5.Luckily, the small ship came back __________ after a big storm. (safe)

6.We couldn't believe that it was her real hair because it was so __________ . (length)

7.Amy's job is to __________ the new machine that was bought last week. (operation)

8.Jane felt nervous when she made her first __________ in front the whole school. (speak)

某石化厂有一种石油产品含有质量分数为4.9%的残余硫酸，过去他们都是用NaOH溶液来清洗这些硫酸．请计算：

（1）若要清洗100kg的这种石油产品，需要______千克的NaOH．

（2）改石化厂进行了技术改造，采用Ca（OH）₂中和这些残余硫酸．每处理100kg这种产品，可以节约______的经费．

NaOH和Ca（OH）₂的市场价格如表：

牙体缺损的修复体，设计时不属非考虑不可的因素是

A．非缺损牙的对颌牙健康情况

B．缺损的部位与缺损的程度

C．缺损牙有无病理性松动

D．缺损牙与对颌牙有无过紧的咬合接触

E．缺损牙的牙周和牙髓情况

通常，路由信息协议(RIP)的跳数小于等于______。

A) 14
B) 15
C) 16
D) 17