commas go where the sentence changes the subject but is still a sentence
Answer:
i'm not sure what the question is. If it is to correct the grammar given, then it would be Mario and Judith <u>a</u><u>r</u><u>e</u><u> </u>studying for <u>a</u><u>n</u><u> </u>upcoming science exam.
I believe it's They believe in your power to choice hope this helps :)
Compound. The simple sentence would be 'they were very busy'
