At which latitude, heat gain through insolation approximately equals heat loss through terrestrial radiation?

The latitude at which heat gain through insolation approximately equals heat loss through terrestrial radiation is around 40° North and South. This is because the amount of solar radiation that reaches the Earth's surface is equal to the amount of terrestrial radiation that is emitted at this latitude. So, the correct answer is option C. Notice that the other options are not correct. The latitude at which the heat gain and heat loss are equal is also known as the "equilibrium latitude".