Which natural event produces oxygen, which can then be used by humans and other organisms

D. when it begins to fall back to the child's handhope i ! > w<

Amutation is basically the change in the gene, caused by alteration of single based units in the dna, or the genes or chromosomes were rearranged in the dna

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.

The first means of speeding up reactions mentioned by the speaker is raising the enzymes