The opioid propeptides

A) include the endorphins and the endomorphins.
B) are made in the terminal button and cleaved by enzymes into the opiate peptides.
C) are processed by proteases into both opiate and non-opioid peptides.
D) are referred to as the "enkephalins."

The correct answer is option C) "are processed by proteases into both opiate and non-opioid peptides".

Explanation:

The opioid propeptides, as well as any other propeptides, is a protein precursor that needs to be excised into a smaller form to acquire its active form.  The opioid propeptides are processed by proteases into both opiate and non-opioid peptides, where the latter could be active or non active. Opiate peptides are enkephalins, endorphins, and dynorphins that act by blocking secondary systems, such as the ones that cause pain perception.