Although mAny pEoplE viEw ConFliCt As BAD, ConFliCt is somEtimEs usEFul ______ it ForCEs pEoplE to tEst thE rElAtivE mErits oF thEir AttituDEs AnD BEhAviors.
A．By whiCh
B．to whiCh
C．in thAt
D．so thAt