The figure shows the P-V plot of an ideal gas taken through a cycle ABCDA. The part ABC is a semi-circle and CDA is half of an ellipse. Then, 

A

the process during the path $$A \rightarrow B$$ is isothermal

B

heat flows out of the gas during the path $$B \rightarrow C \rightarrow D$$

C

work done during the path $$A \rightarrow B \rightarrow C$$ is zero

D

positive work is done by the gas in the cycle ABCDA