Step 1: Understanding somatic reflexes.
In somatic reflexes, which control voluntary movements, the effectors are skeletal muscles. These reflexes involve the nervous system's immediate response to stimuli.
Step 2: Analyzing the options.
(A) skin: Incorrect — Skin is the sensory receptor in reflexes, not the effector.
(B) glands: Incorrect — Glands may be involved in autonomic reflexes, but not in somatic reflexes.
(C) smooth muscles: Incorrect — Smooth muscles are involved in autonomic reflexes, not somatic reflexes.
(D) skeletal muscles: Correct — Skeletal muscles are the effectors in somatic reflexes.
Step 3: Conclusion.
The correct answer is (D) skeletal muscles, as they are the effectors in somatic reflexes.