I whould say A I could be wrong but I think I am right if you feel I am messing with you can report me.
A modifier is an optional element in phrase structure or clause structure, they modify aka. change the meaning of another element in the structure, in this case, the right answer would be letter A.
a) The group members who were working on the project together met on Saturday.
Answer:
It was only 2 units up.
Explanation:
A small increase in the volume would no alert the father of Sangram who is one room away, because that change would only be noticeable for Sangram who is in the same room, but when he doubled the volume from 15 to 30, it was more obvious for his father, one room away, that Sangram was using the remote control and that he was changing the volume in the TV.