In which situation would calcium enter the cell through active transport? O The cell is 20% calcium, and the cell's environment is 80% calcium.
The cell is 50% calcium, and the cell's environment is 50% calcium.
O The cell is 40% calcium, and the cell's environment is 60% calcium.
O The cell is 80% calcium, and the cell's environment is 20% calcium.

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.

the truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey.

sorry, is there a picture? i do not see any arrows.

wut? unius0123 wut?