The analgesic drug ibuprofen `(A)` is chiral and exists in (+) and (-) froms. One enantiomer is physiologically active, while the other is inactive. The other is inactive. The structure of ibuprofen is given below.
The principal functional group in `(A)` is:
A. Pheny1
B. `--COOH` group
C. Isopropy1
D. Both (a) and (b)