Question

L-alanine and D-alanine
A.Are present in virtually all products
B.Are superimposable of each other
C.Are enantiomers
D.Lack and R groups

Answer 1

Alanine (symbol Ala or A) is a -amino acid that is required for protein production. It has a carboxylic acid group and an amine group connected to the central carbon atom, which also has a methyl group side chain.

Complete answer:
Superimposable - Superimposable (superposable): The ability for one object to be placed on top of another, usually so that both are visible. Often used interchangeably with the more general term superposable (the ability for an object to be placed over another object; without the visibility restriction).
Enantiomers - An enantiomer (also known as optical isomer, antipode, or optical antipode) is one of two stereoisomers that are mirror images of each other but are non-superposable (not identical) in chemistry, much like one's left and right hands are mirror images of each other but cannot appear identical simply by reorientation. A single chiral atom or other structural characteristic in a compound causes it to have two non-superposable structures, one of which is a mirror copy of the other.
Enantiomers are molecules that are the exact opposite of one another. Enantiomers are L-alanine and D-alanine.
So, the final answer is option (C) i.e. Are enantiomers.

Note:
Isomers in chemistry are molecules or polyatomic ions that have the same molecular formula — that is, the same number of atoms of each element — but different atomic configurations in space. Isomerism refers to the existence or potential of isomers. Isomers don't always have the same chemical or physical properties as one another.