Which best describes alleles? A
Alleles are the combination of two dominant genes.

B
Alleles are a mutation that occurs during transcription.

C
Alleles are only the physical appearance of an organism.

D
Alleles are the available forms of genes passed to offspring.

c

Explanation:

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers