In which of the following steps of citric acid cycle, `CO_(2)` is evolved
I. Citric acid `rarr alpha`-ketoglutaric acid.
II. Succinic acid `rarr` malic acid III. Malic acid `rarr` oxaloacetic acid IV. `alpha`-Ketoglutaric acid `rarr` succinyl CoA
A. I and II
B. I and IV
C. II and III
D. II and IV