D. involuntary, spindle shaped, uninucleated, tapering
Correct Answer : D.
Smooth muscle is an involuntary, spindle shaped, uninucleated, tapering and non-striated muscle. Smooth muscle is responsible for the contractility of hollow organs, such as blood vessels, the gastrointestinal tract, the bladder, or the uterus. Its structure differs greatly from that of skeletal muscle, although it can develop isometric force per crosssectional area that is equal to that of skeletal muscle. However, the speed of smooth muscle contraction is only a small fraction of that of skeletal muscle.