Answer:
use a comma yo set off aphrase or a clause at the beginning of a sentence
Answer:
B would be the correct answer
Explanation:
Use a comma to set off a phrase or clause at the beginning of a sentence. As you can see, 'In their homeroom classes' is just the beginning of the sentence and it just show the location and normally, after the comma in this situation if the main topic of the sentence so B would be the correct answer.
Hope this help you :3