Which amino acids have a polar side chain but are not aromatic?

The amino acids with polar side chains that are not aromatic can be identified by their chemical structures and properties. Serine, threonine, and asparagine all possess polar side chains due to their functional groups, which can interact favorably with water.

Serine contains a hydroxymethyl group (-CH2OH), making it polar and hydrophilic. Threonine has a hydroxyl group as well as an additional methyl group, also contributing to its polarity without any aromatic characteristics. Asparagine features an amide group (-C(=O)NH2) in its side chain, which is polar and does not contain any aromatic rings.

In contrast, the other options include at least one amino acid with an aromatic side chain or side chains that do not meet the criteria of being polar without aromaticity. Considerations of each side chain's polarity and structure are critical in determining the correct answer. Therefore, serine, threonine, and asparagine are the correct answer as they collectively fit the criteria of being polar with non-aromatic side chains.