Question $14(2\mathrm{.}5$ points$)$

Which of the following is true?

Tryptophan is an essential amino acid with a carbon skeleton that can be used to form glucose, but it cannot be used to form ketone bodies.

Alanine is an essential amino acid with a carbon skeleton that can be used to form both ketone bodies and glucose.

Leucine is an amino acid with a carbon skeleton that can be used to form glucose, but it cannot be used to form ketone bodies.

Valine is an essential amino acid with a carbon skeleton that can be used to form glucose, but it cannot be used to form ketone bodies.