Questions

When exports are greater than imports, net exports are positive and similarly, when imports are greater than exports, net exports are negative.

When a country imports goods, it buys them from foreign producers. The money spent on imports leaves the economy, and that decreases the importing nation's GDP.

Ozone layer depletion is one of the most serious problems faced by our planet earth. Substances that Deplete the Ozone Layer (ODS) emission are responsible for ultraviolet radiations from the sun break them to release chlorine (from CFCs) and bromine (from methyl bromide and halons).

When heated any substance, the molecules move apart from each other. Alike in the air the molecules move apart from each other. We know that the warm air is lighter than the cool air. Since after heating air gets warmer, it floats up and the cool air comes down to occupy the warm air place.