Glycine is a highly conserved amino acid residue in proteins (i. e., it is found in the same position in the primary structure of related proteins). Which of the following reasons is the most likely explanation for this observation

Glycine contains a lone hydrogen atom in its side group which makes it less bulky than other amino acids

Explanation:

Glycine contains a lone hydrogen atom in its side group which makes it less bulky than other amino acids. This characteristic enables it to overcome strict effects or nonbinding barriers which be faced by other amino acids

i'd say that the moon rock is about 2.2 billion years old.