This change from fins on the love-finned fish to legs and feet on the early amphibian is most likely due to:.
1. a sudden mutation that changed the gills of the lobe-finned fish to lungs
2. the need to move to land because of increased competition for food in the ocean
3. increased competition between animals that had adapted to living on the land
4. variations among offspring, followed by natural selection

Explanation:

Lobe-finned fishes are bony fish, having fleshy, lobed, paired fins, these fins are joined to the body by a single bone only . The fins of these lobe-finned fishes differ from all other fishes in many ways, Lobe-finned fish lived in water.

By the passage of time, from fin on lobe-finned fish changed to legs and feet on the early amphibians due to variations among offspring, followed by natural selection. These  legs and feet containing amphibians lives both in water and land.

significant amounts of nitrogen oxides, carbon monoxide, and other pollution

explanation:

passenger vehicles are a major pollution contributor, producing significant amounts of nitrogen oxides, carbon monoxide, and other pollution. in 2013, transportation contributed more than half of the carbon monoxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into our air.

frogs. the lower the ph the higher the acid content. frogs have the highest tolerance in this scenario.