（1）当and连接并列主语时，谓语动词通常用复数形式。
eg：
Baker and Mary are interested in history. 贝克和玛丽对历史感兴趣。
Plastic and rubber never rot. 塑料和橡胶不会腐烂。
（2）当由and连接的两个并列主语前面有each，every， no修饰时，谓语动词用单数形式：
eg：
Every boy and (every) girl likes the puppy. 每个男孩女孩都喜欢这只小狗。
No desk and (no) chair was seen in the room. 房间里不见桌椅。
（3）由and连接的两个词语表达同类概念时，谓语动词通常要用单数，这时and后面的名词前面通常没有冠词。
eg：
A cart and horse was seen in the distance. 远处看见一辆马车。
A knife and fork is on the table. 桌上摆着一副刀叉。
A needle and thread was found in the floor. 在地板上找到了针线。
扩展资料：
常见用and连接是表达同一概念的词组：
law and order 法制 soap and water 肥皂水
a cup and saucer 茶杯碟子 fork and knife 刀叉
the needle and thread 针线 trial and error 反复尝试，不断摸索
horse and carriage 马车 time and tide 岁月
bread and butter 奶油面包 the ebb and flow 盛衰，潮涨潮落
参考资料：
lin and tom's baby + is
lin and tom's babies + are