Read the text to complete the gaps,
Rain becomes acid when power stations, factories, and cars are 1(are emitting; emit; emitted) their toxic fumes into the
atmosphere. The polluted air mixes 2(with; by; to) water, oxygen, and other chemicals to form acids. These then
combine with water and other materials into clouds before falling 3(on; to; down) the ground. Winds can blow
4(polluting; pollution; polluted) clouds over long distances and across borders making acid rain a problem for everyone and n
just those who live close 5(by; to; near) these sources.
