Which of the following statements is true about the interaction of sympathetic and parasympathetic nerve fibers?
a) Sympathetic and parasympathetic nerve fibers may innervate the same organs, but they have generally opposite effects.
b) Both types of nerve fibers use the same neurotransmitter.
c) Sympathetic nerve fibers innervate some internal organs; parasympathetic fibers innervate other internal organs.
d) Sympathetic nerve fibers are more active when the body is at rest; parasympathetic fibers are more active during emergencies.
