是否所有的并列句都必须有并列连词？

是的
并列句中的分句通常用一个并列连词来连接,其中的各分句意义同等重要,联系密切,无从属关系。使用时要特别注意其连词特性。

1.由and,not only...but(also)...,neither,nor,neither...nor...等词连接的并列句,在意义上主要对前一句作补充或引伸,包括肯定和否定两方面意义。

1)and连接并列句表示意义的增补、动作的先后、条件和结果等。例如:

One day John was late,and his teacher was angry.

The car broke down halfway,and they had to stay in a small inn for the night.

Think it over,and you'll find a way out.

2)not only...but(also)...表示"不但……而且",重点强调的是后一部分。例如:

Not only is he himself interested in the subject,but also his students began to show interest in it.

Not only is your answer right,but mine also is.

3)neither...nor...,nor,neither等表示否定意义的引伸,放在句首要倒装。例如:

Neither does he work hard,nor does his brother.Mr. Wang doesn't smoke,neither/nor does Li Ping.

2.or,either...or...连接并列句表示选择意义。

1)or常表示选择、换个说法、否定条件等意义。例如:

The children can go with us,or they can stay in.(选择)
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