Question

When is it appropriate to break the rule that requires subjects joined by and to use a plural verb?

Answer 1

In English language, if two subjects are joined by the word 'and', then the plural form of the appropriate verb has to be used in the sentence.
For instance: Tom and Jerry ARE friends. 'ARE' is an example of plural form of verb.
 But if it happens that the two subjects, that are joined by 'and' refer to the same thing or  the same person, then the singular form of the appropriate verb will have to be used. For instance: Beans and corn IS a popular dish in Nigeria during the rainy season. The verb 'IS' shows that the food beans and corn refers to a single food. 

Answer 2

Answer:

It is appropriate to break the rule that requires subjects joined by and to use a plural verb on three occasions. When the parts of the subject refer to a single person, place, thing or idea, they require a singular verb.

Explanation: