28.
A:
A Ca2+ calmodulin complex activates the phosphatase that causes contraction of smooth muscle.
B:
Unlike straited muscle, contraction of smooth muscle cells occurs when Ca2+ levels fall.
C:
Phosphorylation of a myosin light chain allows actin-myosin binding in smooth muscle.
D:
Dephosphorylation of a myosin light chain allows actin-myosin binding in smooth muscle.
The answer is: C