Which of the following amino acids has two chiral centers? Identify the two chiral centers using an asterisk (*).

Chemical structure of another amino acid with two chiral centers marked by asterisks.

Chemical structure of a third amino acid with two chiral centers marked by asterisks.

Chemical structure of a fourth amino acid with two chiral centers marked by asterisks.

Chemical structure of a fifth amino acid with two chiral centers marked by asterisks.