Answer:
The correctly written sentence in the group is:
b. I like to listen to rock music while I do my homework
Step-by-step explanation:
In the sentence (a) the conjunction is missing. A conjunction is a word which joins two words or sentences. The word 'while' is used as a conjunction to join the two sentences. In the sentence (b) the two sentences are joined by the conjunction 'while' which helps in making complete sense of the sentence.