Work 1→2 Work 2→3 Work 3→4 Work 4→1
A. W > 0; W = 0; W < 0; W = 0
B. W < 0; W = 0; W > 0; W = 0
C. W = 0; W > 0; W = 0; W < 0
D. W = 0; W < 0; W = 0; W > 0
Answer:D
Work 1→2 Work 2→3 Work 3→4 Work 4→1
A. W > 0; W = 0; W < 0; W = 0 B. W < 0; W = 0; W > 0; W = 0 C. W = 0; W > 0; W = 0; W < 0 D. W = 0; W < 0; W = 0; W > 0