In what way is a neuropeptide intermediate between neurotransmitters and hormones?

a. A neuropeptide diffuses more widely than other neurotransmitters but less than a hormone.

b. A neuropeptide is larger than other neurotransmitters but smaller than a hormone.

c. A neurotransmitter produces excitatory effects, a neuropeptide produces neutral effects, and a hormone produces negative effects.

d. A neurotransmitter produces slow effects, a neuropeptide produces faster effects, and a hormone produces still faster effects.