The farm as well as its neighboring hills which we once spent so

much time ______ on a new look as recently as last year. [ ]

A. on has taken

B. has taken

C. on having taken

D. having taken

如图所示p-V图中，一定质量的理想气体由状态A经过ACB过程至状态B，气体对外做功280J，放出热量410J；气体又从状态B经BDA过程回到状态A，这一过程中气体对外界做功200J．

求：（1）ACB过程中气体的内能是增加还是减少？变化量是多少？

（2）BDA过程中气体是吸热还是放热？吸收或放出的热量是多少？