Which of the following sentences needs a comma to be correctly punctuated?
my mother writes and edits for a major publication.
my mother and my father edit a gardening magazine.
my mother writes for a magazine and my father edits novels.
my mother writes for a magazine that my father edits.

The sentence that needs a comma to be correctly punctuated is the third one - My mother writes for a magazine and my father edits novels-

The correct punctuation would be - My mother writes for a magazine, and my father edits novels-

This is a clear example of a compound sentence.

Compound sentences have at least two independent clauses and are linked by a coordinating conjunction, such as: for, and, but, yet, etc. In this case, they are linked by the conjunction AND.

We use a comma before the conjunction that connects the two independent clauses.

need water need food need shelter need air need money want cars want games want tv want cable

explanation:

your answer is c) experiments with water vapor showed that elements combine in specific proportions.