Chapter 13, Problem 16RA

During the phase of isovolumetric relaxation of the ventricles, the pressure in the ventricles is

$\begin{array}{l}\text{a}\text{. rising}\text{. }\\ \text{b}\text{. falling}\text{. }\\ \text{c}\text{. first rising, then falling}\text{. }\\ \text{d}\text{. constant}\end{array}$