For the first question, the answer would be D. (It supports the idea that living in a foreign country is the smartest way to learn a new language)
D: Language researchers found that students who lived in a foreign country learned the new language sixty-five percent faster than students learning at home.
The counterclaim is something that counteracts the statement. Therefore, for the second questions, the answer should be B.
B: However, learning to play an instrument has been proven to improve grades and test performance.
I think it could be six but if you mean their is 3 more dancers added then it would be 9 singers
