A variety of smooth muscle relaxants can promote the occurrence of Ca⁺⁺ sparks beneath sarcolemma of smooth muscle.The Ca⁺⁺ sparks are thought to originate from a local activation of the ryanodine receptor,just beneath the sarcolemma.These Ca⁺⁺ sparks promote relaxation by:

A)Activating the Na⁺-Ca⁺⁺ antiporter in the smooth muscle.
B)Activating the Ca⁺⁺-dependent phosphatase calcineurin in the smooth muscle.
C)Activating Ca⁺⁺-dependent K⁺ channels in the smooth muscle.
D)Promoting myosin light-chain phosphorylation in the smooth muscle.
E)Activating Rho kinase in the smooth muscle.