A girl holds her breath for 30 seconds, breathes out, and then breathes in. Compared with the air she breathes out, the air she breathes in contains less A) carbon dioxide and water vapour
B) nitrogen and water vapour.
C) oxygen and carbon dioxide.
D) oxygen and nitrogen.​

sulfur dioxide

explanation: acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. these substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation: