Endorphins are neurotransmitter molecules similar to

A) dopamine.
B) serotonin.
C) morphine.
D) acetylcholine.

Endorphins are similar in structure and function to morphine, as they both act as painkillers and produce feelings of pleasure and euphoria. They bind to opioid receptors in the brain, just like morphine does. While dopamine and serotonin are also neurotransmitters that play key roles in mood and pleasure, they are not structurally similar to endorphins in the same way that morphine is. Acetylcholine is a neurotransmitter involved in muscle contraction and cognitive function, but it does not play a significant role in pain relief or pleasure.