The number of bonding pairs of electrons on the central carbon atom is 4.
The central atom in ethanol is carbon (C). To determine the number of bonding pairs of electrons on the central atom, we count the number of bonds formed by carbon. In this case, carbon forms four sigma (σ) bonds with hydrogen (H) and oxygen (O).
Each single bond represents one sigma bond, and since there are four single bonds in ethanol, there are four sigma bonds around the carbon atom. Therefore, the number of bonding pairs of electrons on the central carbon atom is 4.