闭合导线ABCD，已知横坐标增量△YAB=120.36m, △YCB=60.01m, △YCD=20.52m, △YDA=-80

闭合导线ABCD，已知横坐标增量△YAB=120.36m, △YCB=60.01m, △YCD=20.52m, △YDA=-80.73m,则fy为（）

A.+79.21m

B.-0.05m

C.-79.21m

D.+0.05m

正确答案是D