Eating foods that boost levels of the neurotransmitter serotonin serves to

Improve mood

It also helps with sleep, memory, digestion, appetite.

Explanation:

It has been demonstrated that the consumption of food with high levels of tryptophan, an amino acid that plays a major role in serotonin production in the brain, improves the mood considerably and other benefits as well.

Serotonin is a neurotransmitter and chemical that plays a role in mood, memory, behavior, appetite, digestion, sleep, amongst many other activities. It is also known as the key neurotransmitter for happiness. The absence of this neurotransmitter could lead to severe disorders, such as depression.

Therefore, eating foods that boost levels of serotonin, such as salmon, spinach, and nuts, serve to improve mood, sleep patterns, memory, etc.

b and c would be the answers

out of the choices i'd say d the ability to set goals, mainly because to desire to continue you need motivation but it isn't motivation in that part, but setting goals means you have an endgame and you want to reach it which sums up motivation.