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 rarr B ` is isothermal
B. heat flows out of the gas during the path `B rarr C rarrD`
C. work done during the path `A rarr B rarr C` is zero
D. positive work is done by the gas in the cycle `ABCDA`