Alow-pressure belt means the air is
a) cold and dry
b) warm and rising
c) cold and sinking
d) warm and moist

The correct answer is b) warm and rising

The air pressure is defined as a force applied in every direction by all the air above a place. Air expands on heating and it gets compressed on cooling. Expansion and compression of air results in variations in the atmospheric pressure. At low pressure belt, air is warm due to heating and warm air expands and rises.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."