(N/A) The nature of the chemical reaction occurring on a $C=C$ bond or $C=O$ bond can be explained based on the polarity of the bond.
In a carbonyl group $(C=O)$,the oxygen atom is more electronegative than the carbon atom. This creates a dipole where the carbon acquires a partial positive charge $(+\delta)$ and the oxygen acquires a partial negative charge $(-\delta)$. Due to this electrophilic carbonyl carbon,these compounds undergo nucleophilic addition reactions.
On the other hand,in alkenes $(C=C)$,the bond is non-polar because both atoms have the same electronegativity. The $\pi$-electron cloud is electron-rich,making the $C=C$ bond nucleophilic in nature. Therefore,alkenes undergo electrophilic addition reactions.