Which one has the highest percentage of nitrogen?

Mass percentage of $C, H$ and $O$ in a compound are $60\%$,$13.33\%$ and $26.67\%$ respectively. The molecular weight of the compound is $60$. The molecular formula of the compound is

An oxide of copper which is red in colour has the formula

An organic compound has an empirical formula $CH_2O$,its vapour density is $45$. The molecular formula of the compound is

$A$ hydrocarbon contains $10.5 \, g$ of carbon and $1 \, g$ of hydrogen. If the volume of $2.4 \, g$ of this hydrocarbon is $1 \, L$ at $127 \, ^\circ C$ and $1 \, atm$ pressure,then the hydrocarbon is:

An oxygen-containing organic compound was found to contain $52 \%$ carbon and $13 \%$ hydrogen. Its vapour density is $23$. The compound reacts with sodium metal to liberate hydrogen. $A$ functional isomer of this compound is