Which hydrogen in formic acid is the acidic hydrogen?

Answer 1

(A) HA O
(B) HB HA - C - O - HB

I forgot to add this part

Answer 2

Formic acid is H2CO2. Structurally that is HCOOH. The acidic H is the one on the right side; i.e., the H on COOH. In organic chemistry the -COOH groups are acidic and it's the H that is the acidic H.