Which of the following describes carbachol's qualities?

• A. Resistant to hydrolysis and non-selective
• B. Rapidly hydrolyzed and selective for nicotinic receptors
• C. Predominantly muscarinic selective
• D. Non-therapeutic and inactive

Answer: (A)

The main idea here is how cholinergic agonists differ in how long they last and which receptors they activate. Carbachol behaves like acetylcholine in that it stimulates cholinergic receptors, but it is different in two key ways: it is resistant to hydrolysis by acetylcholinesterase, so its effects persist longer, and it is non-selective, meaning it activates both muscarinic and nicotinic receptors. That combination—longer duration due to hydrolysis resistance and broad receptor activation due to non-selectivity—fits the description of being resistant to hydrolysis and non-selective. The other statements clash with carbachol’s actual profile: it isn’t rapidly hydrolyzed, it isn’t selective for nicotinic receptors, it isn’t predominantly muscarinic, and it can be used therapeutically in clinical settings (for example, in ophthalmology).