Which of the following statements is a valid generalization regarding the properties of smooth muscle?a) Neurotransmitters can either excite or inhibit smooth muscle contraction but any given neurotransmitter is always excitatory or inhibitory regardless of where the muscle is locatedb) A given smooth muscle call can respond to more than one type of neurotransmitterc) Smooth muscle cells are generally unresponsive to neurotransmitters of all typesd) Smooth muscle cells can respond to neural input from the somatic or autonomic nervous systemse) all of the above
