2) 分号
They live on the first floor ; we live on the second. (对比)
Everyone was late ; the snow had caused a traffic jam. (补充说明)

3) 分号+连接性副词+逗号
We didn’t like the choice ; however , we had to accept it.
We didn’t know what to do ; therefore , we did nothing.
适用于这种情况的连接性副词还有：consequently，furthermore，moreover，nevertheless等。

注：ⅰ）连接性副词位于句末时，前面一般用逗号，后面用句号。例如：
The new seats in the auditorium are more comfortable; the acoustics are worse , however.
ⅱ) 连接性副词也放在句首，后面用逗号。例如：
I hadn’t read the test very carefully. Therefore , I was surprised that I had done so well.
I hadn’t read the test very carefully ; therefore , I was surprised that I had done so well.
ⅲ)  then 和thus后面不用逗号。例如：
The ice cracked and split ; then that boy sank into the bone-chilling water.

EXERCISE 2
Punctuate the following sentences:
1．The plan won’t work for there are too many things wrong with it.
2．The bus broke down as a result we were late for work.
3．Martin left a note it said he would be late.
4．This is a new watch yet it doesn’t work.
5．Jim was very tired so he went right off to sleep.
6．Business was booming consequently the company needed more workers.
7．The sky was bright blue with a few white clouds in it and it was a beautiful day for the picnic.
8．The dining hall is nice looking the food however is terrible.
9．Attendance is compulsory the students have no choice therefore.
10．Some people put cream and sugar in their coffee others prefer it black.
11．Space exploration is costly nevertheless we must continue to spend money on space travel if we are to learn about our universe.
12．Astronauts are affected by weightlessness moreover they are also affected by boredom and loneliness.