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A.b1a过程放热，做负功；b2a过程放热，做负功 B.b1a过程吸热，做负功；b2a过程放热，做负功 C.b1a过程吸热，做正功；b2a过程吸热，做负功 D.b1a过程放热，做正功；b2a过程吸热，做正功
题目
A.b1a过程放热，做负功；b2a过程放热，做负功
B.b1a过程吸热，做负功；b2a过程放热，做负功
C.b1a过程吸热，做正功；b2a过程吸热，做负功
D.b1a过程放热，做正功；b2a过程吸热，做正功
B.b1a过程吸热，做负功；b2a过程放热，做负功
C.b1a过程吸热，做正功；b2a过程吸热，做负功
D.b1a过程放热，做正功；b2a过程吸热，做正功