Final answer:
In English grammar, 'Sam and Chris' are considered a plural subject because they are two individuals connected by 'and,' hence 'don't' is the correct verb to use, not 'doesn't.' 'Doesn't' is used with singular subjects, while 'don't' is used with plural subjects to maintain proper subject-verb agreement.
Step-by-step explanation:
The question you're asking involves the subject-verb agreement in English grammar. When we have two subjects connected by 'and,' we treat them as a plural entity, which is why we use 'don't' rather than 'doesn't.' The verb 'doesn't' is only used with singular nouns or pronouns, such as 'he,' 'she,' or 'it,' or with singular proper nouns. Since 'Sam and Chris' are two people, they are considered a plural subject and therefore the correct verb to use is 'don't' as in 'Sam and Chris don't know many people.'
This rule is part of proper English grammar conventions which help ensure that the subject and verb in a sentence agree in number. It is important not only for speaking but also for writing clearly and correctly. When constructing sentences with compound subjects, it's essential to choose the correct verb form to maintain subject-verb agreement.