When should a comma be used?

A. to create a pause

B. to change the subject

C. to end a sentence

D. to build suspense

A. to create a pause

Commas are used to indicate a pause in a sentence, separate items in a list, separate clauses, or to set off certain elements within a sentence. They do not change the subject, end a sentence (that is the role of a period), or build suspense.