Which sentence has correct punctuation?

A. I have always wanted to become a veterinarian but I don’t do very well in science and math classes.

B. I have always wanted to become a veterinarian but, I don’t do very well in science and math classes.

C. I have always wanted to become a veterinarian, but, I don’t do very well in science and math classes.

D. I have always wanted to become a veterinarian, but I don’t do very well in science and math classes.

Respuesta :

The answer should be D. They are both independent clauses and can stand alone, so you would put a comma before "but". 

Answer:

D. I have always wanted to become a veterinarian, but I don’t do very well in science and math classes.

Explanation:

When coordinating conjunctions are used between two complete sentences (independent clauses), a comma will be needed before the coordinating conjunction.  If a comma is missing before the conjunction between two complete sentences, then you will have the error of a run-on sentence.  If what followed the conjunction happened to not be a complete sentence, then no comma would have been needed.