What is the $IUPAC$ name of Mesityl oxide?

In aldehydes and ketones,the carbon atom of the carbonyl group is

In column-$I$,diagrams of the carbonyl group are given,and in column-$II$,their descriptions are given. Match column-$I$ with the correct option given in column-$II$.
| Column-$I$ (Drawing diagram) | Column-$II$ (Description) |
| :--- | :--- |
| $(A)$ Resonance structures of carbonyl group | $(i)$ In carbon-oxygen,$\pi$-electron clouds are present on the upper and lower parts of the plane. |
| $(B)$ Geometry of carbonyl group | (ii) Non-bonding $2p$ orbital which is not taking part in hybridization of carbonyl carbon and $2p$ orbital of oxygen containing one electron are parallel to each other and perpendicular to the plane. |
| $(C)$ $\sigma$-bonding in carbonyl group | (iii) Hybridization of carbonyl carbon is $sp^2$ and it has a planar triangular structure and bond angle approximately $120^{\circ}$. |
| $(D)$ $\pi$-bonding in carbonyl group | (iv) Two hybrid structures of the carbonyl group indicate that the carbon-oxygen bond is polar in nature and also the carbon atom is an electrophilic centre and the oxygen atom is a nucleophilic centre. |

The $IUPAC$ name of the given compound is:

Give the name and structure of the following compounds:
$(i)$ Methanal $(ii)$ Ethanal $(iii)$ $2$-Methylpropanal $(iv)$ $3$-Methylcyclohexanecarbaldehyde $(v)$ $2$-Methoxypropanal $(vi)$ Pentanal $(vii)$ Prop-$2$-enal $(viii)$ Benzene-$1,2$-dicarbaldehyde $(ix)$ $3$-Bromobenzaldehyde

Formalin is an aqueous solution of which of the following?