Chapter 18, Problem 15RA

Which of these statements about contraction of intestinal smooth muscle is true?

$\begin{array}{l}\text{a}\text{. It occurs automatically}\text{.}\hfill \\ \text{b}\text{. It is increased by parasympathetic nerve stimulation}\text{.}\hfill \\ \text{c}\text{. It produces segmentation}\text{.}\hfill \\ \text{d}\text{. All of these are true}\text{.}\hfill \end{array}$