Step 1: Looking at the R group of each amino acid helps identify the methyl-bearing one. Glutamine's R group ends in an amide (-CONH2), tryptophan's R group is a large indole ring system, and tyrosine's R group is a benzene ring with an attached hydroxyl (phenolic) group.
Step 2: Alanine, by contrast, has the simplest possible side chain of the group, just a single methyl group attached to the central carbon, making it one of the smallest, nonpolar amino acids.
Step 3: Because a methyl group side chain specifically describes alanine and none of the other three, the correct answer is Alanine.