The correct answer is option 4 - Heating of glass surface of a bulb due to current in filament.

Convection is the transfer of heat through the movement of a fluid, either gas or liquid. In option 1, boiling water, convection plays a significant role as the heat is transferred from the bottom of the pot to the water molecules, causing them to rise and create a circulation of heat.

In option 2, land and sea breeze, convection is involved as the uneven heating of land and water causes the air near the surface to rise, creating a breeze.

In option 3, the circulation of air around a blast furnace, convection is again the main mechanism of heat loss. The hot air rises, drawing in cooler air, and creates a continuous convection current.

Option 4 is different because it involves the heating of a glass surface of a bulb due to the current in the filament. In this case, heat is primarily transferred through conduction, which is the transfer of heat through solids or direct contact. The electrical current passes through the filament, generating heat, which is then conducted to the glass surface of the bulb.