Final answer:
Levels of oxytocin decreases during affection.
Step-by-step explanation:
The brain chemical that decreases during affection is Levels of oxytocin. Oxytocin is often referred to as the “love hormone” because it is associated with social bonding and feelings of trust and affection. When people experience affection, the levels of oxytocin in their brain decrease.
On the other hand, Levels of dopamine tend to increase during affection. Dopamine is a neurotransmitter that is involved in the brain's reward system and is associated with pleasure and motivation. Additionally, the level of cortisol, a stress hormone, also tends to decrease during affection.
Therefore, the correct answer to the question is C: Levels of oxytocin.