Which of the following compounds contains most acidic hydrogen ?
A. `H_(3)C-overset(O)overset(||)C-H`
B. `H_(3)C-overset(O)overset(||)C-CH_(2)-overset(O)overset(||)C-CH_(3)`
C. `H_(3)C-overset(O)overset(||)C-CH_(2)-overset(O)overset(||)C-OCH_(3)`
D. `H_(3)C-overset(O)overset(||)C-CH_(2)-overset(O)overset(||)C-overset(..)NH_(2)`