Be good at和Do well in的区别.

Be good at和Do well in的区别.
一道选择题：
-I ____ singing when I was a student. What about you,Rose?
-I couldn't sing at all, but I ____ dancing and playing the piano.
A.am good in;do well at
B.do well in;am good at
C.was good at;did well in
D.did well at;was good in
要解释下、、