The ants， hardworking _______ they are， have their time for play

The ants， hardworking _______ they are， have their time for play.
A、if
B、as
C、since
D、though
【正确答案】：B
【题目解析】：hardworking as they are 部分倒装，原句为as they are hardworking。因此选B.