A client is experiencing a cholinergic crisis after being administered pyridostigmine IV. The nurse should administer which of the following reversal agents?

A. Galantamine is a reversible acetylcholinesterase inhibitor and would not be effective in treating a cholinergic crisis. B. Physostigmine is also a reversible acetylcholinesterase inhibitor and would not be suitable for reversing a cholinergic crisis. C. Flumazenil is a benzodiazepine antagonist used to reverse benzodiazepine effects, not cholinergic crises. D. Atropine is an anticholinergic medication that is effective in reversing the effects of excessive acetylcholine during a cholinergic crisis, making it the appropriate choice in this situation.