Question

What is the oxidation number of underlined element?

$\underset{–}{C}{H}_{2}O$

Answer 1

Let $x$ be the oxidation number of $C$ in $\underset{–}{C}{H}_{2}O$.
Since the overall charge on the compound is $0$, the sum of oxidation states of all elements in it should be equal to $0$.
Therefore, $x+2(+1)-2=0$
Hence, $x=0$
Hence, the oxidation number of $C$ in $\underset{–}{C}{H}_{2}O$ is $0$.