g when hydrogen is present and the citric acid cycle is active, the ph of the mitochondrial matrix is

The pH remains constant

Explanation:

The pH value of Mitochondrial matrix = 7.8 while the pH of the intermembrane space of the mitochondria = 7.0–7.4

The presence of the hydrogen atoms makes the mitochondrial matrix acidic and hence reduced the pH value but the pH of inner and outer matrix is maintained equal to each other thus as the H+ ion increases, the base concentration increases thereby pushing H+ to the inter membrane space and hence producing ATP.

the last one: artificial selection/genetic engineering

plant breeding is modifying the genetic composition of the plant - but this isn't cloning (which is specifically introducing a gene into a genome). but you are artificially selecting for the phenotype that you want.

the second one is literally genetic engineering - the gene would have been cloned first and then inserted or genetically engineered into the new plant cell (the cotton).