Which sentence best shows correct comma usage?

a.
he graduated from college, and he got his diploma.

b.
he graduated from college, and, he got his diploma.

c.
he graduated from college and, he got his diploma.

d.
he, graduated from college, and he got his diploma.

The sentence that shows correct comma usage is A.

Explanation:

Sentence A is a clear example of the use of a comma before the coordinatinating conjunction and. When two independent clauses are joined by a coordinating conjunction, a comma is required before the conjunction. Otherwise, the sentence becomes a run-on sentence.

An independent clause is clause that represents a complete thought, and can therefore stand alone as a sentence (1 & 2).

1) He graduated from college,

2) And he got his diploma

where is the

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