What effect does sympathetic activation have on the pupil?

What effect does sympathetic activation have on the pupil?

• A. Pupil constriction via contraction of the sphincter pupillae.
• B. Pupil dilation via contraction of the dilator pupillae, driven by acetylcholine on muscarinic receptors.
• C. Pupil dilation due to parasympathetic activation of the ciliary muscle.
• D. Pupil dilation via contraction of the radial iris muscle (dilator pupillae) due to norepinephrine on adrenergic receptors.

Answer: (D)