Answer :
Answer:
The answer is: A good sentence.
Explanation:
The above statement is made up of two independent clauses. This means that each of those clauses make complete sense.
Breaking them up will be: "Miss Smith kept both of them after school."
"They hadn't done their homework."
If a comma was in between them(comma splice), it would have been wrong because the statements can stand on their own.
To use two independent clauses together in a statement, a conjunction must be used as it is in the text above ( "because" was used). Using a conjunction, a sensible idea is communicated without losing meaning of any one and the statement as a whole is considered a good sentence.