Working down mate, my best answer would be carbon monoxide, but I'm not studying exactly what you are. All those answers are logical except ozone.
Variations in evolution usually refers to variation of genes at a particular loci. This differs from diversity which is the total of genetic differences within a population. Speciation is the reproductive isolation of a subset of a population.
Obligate symbiotic fungi that form associations with plants by entering their cortical cells without invading the plant cells membrane are called endomycorrhizae and include the genus Glomus. Many plants form associations called mycorrhizae with fungi that give them access to nutrients in the soil, protecting against disease and toxicities. In these associations the fungi are integrated into the physical structure of the root, where the fungi colonize the living root tissue during active plant growth.
A. because the heart will pump more blood filled with oxygen to the muscles that need it most
