\textbf{211-} If in the methanol molecule, the oxygen atom is replaced by the group $\mathrm{C=O}$, which compound is obtained and how many electrons in that molecule participate in pi bonding?
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(1) Ketene $-$ 6 \qquad (2) Ketene $-$ 4 \qquad (3) Methanoic acid $-$ 6 \qquad (4) Methanoic acid $-$ 4
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