根据句意和汉语提示，填写恰当的短语完成下列句子。

1. _____ (首先), the computer room must be kept clean.

2. _____ (有时) he goes to the English club after school.

3. Too much work and too little rest can _____ (引发) illnesses.

4. I am happy that I bought the computer _____ (以最低的价格).

5. This book is specially _____(针对) teenagers.

写出磁通密度的SI单位与CGS单位制之间的换算关系：1T=（）GS，空气中磁感应强度和磁场强度的关系是（）。