Which of the following drugs has muscarinic and nicotinic actions and is resistant to hydrolysis by both true and pseudo cholinesterase:

Correct Answer: B

Rationale: Step-by-step rationale for why B (Carbachol) is the correct answer: 1. Carbachol is a cholinergic drug that acts on both muscarinic and nicotinic receptors. 2. It is resistant to hydrolysis by both true and pseudo cholinesterase enzymes. 3. Acetylcholine (A) is rapidly hydrolyzed by both cholinesterases. 4. Bethanechol (C) is a muscarinic agonist but not a nicotinic agonist. 5. Succinylcholine (D) is a depolarizing neuromuscular blocking agent, not a cholinergic agonist. Summary: Carbachol is the only drug among the choices that has both muscarinic and nicotinic actions and is resistant to hydrolysis by cholinesterases. Acetylcholine is rapidly hydrolyzed, Bethanechol does not have nicotinic actions, and Succinyl

Correct Answer: D

Rationale: The correct answer is D. Atropine blocks the effects of cholinesterase inhibitors on muscarinic receptors but not on nicotinic receptors, which are responsible for skeletal muscle overstimulation. Atropine can block bronchoconstriction, increased bladder activity, and increased bowel motility as they are mediated by muscarinic receptors. Therefore, the effects on skeletal muscle overstimulation, leading to paralysis, will not be blocked by atropine.

Correct Answer: A

Rationale: The correct answer is A because labetalol is unique among most β-blockers as it also blocks alpha-adrenergic receptors. This dual action results in vasodilation and reduced blood pressure. Choice B is incorrect as labetalol does not cause atropine-like side effects. Choice C is incorrect as labetalol blocks both β1 and β2 receptors. Choice D is also incorrect as labetalol does have some β2 blocking activity, making it not entirely safe for asthmatics.

Correct Answer: B

Rationale: The correct answer is B: 1 and 2 only. Sentence 1 and 2 are correct because they are grammatically accurate and logically coherent. Sentence 3 is incorrect as it contains a grammatical error. The key is to analyze each sentence independently to determine its correctness based on grammar, clarity, and logical consistency. In this case, only sentences 1 and 2 meet the criteria, making B the correct choice.

Correct Answer: A

Rationale: The correct answer is A because an endothermic reaction absorbs thermal energy from the surroundings to proceed. In an endothermic reaction, the products have higher potential energy than the reactants, requiring energy input. Choice B is incorrect as endothermic reactions do not transfer thermal energy to the surroundings. Choices C and D are incorrect as they describe exothermic reactions, where thermal energy is released to the surroundings.