Сопоставление предложений и ответов:
- 1 - a (Are you free tonight? - I think so.)
- 2 - b (Would you like to join me? - Count me in!)
- 3 - c (What about a pop concert? - Pop music is not really my thing.)
- 4 - d (How about a pizza? - No, thanks.)
Ответ: 1-a, 2-b, 3-c, 4-d.