A:a<b<c
B:a<c<b
C:b<c<a
D:b<a<c
如图所示,A、B两闭合线圈为同样导线绕成,A有10匝,B有20匝,两圆线圈半径之比为2:1.均匀磁场只分布在B线圈内.当磁场随时间均匀减弱时( )
make up one's mind; give in; ever since; be fond of; grow up: on schedule; change one's mind ;care about; prefer to; get sb. interested in