Selective β2 agonists produce all of the following EXCEPT:

Correct Answer: D

Rationale: The correct answer is D: Stimulate uterine contraction. Selective β2 agonists primarily target β2 receptors in the lungs, leading to bronchodilation. They have minimal effect on β1 receptors, thus do not significantly impact heart rate or blood pressure. However, β2 receptors in the uterus can cause uterine relaxation, not contraction. Therefore, selective β2 agonists do not stimulate uterine contractions. Choices A, B, and C are incorrect as they align with the typical effects of selective β2 agonists.

Correct Answer: C

Rationale: Correct Answer: C Rationale: 1. Phenylephrine is a vasoconstrictor that raises blood pressure. 2. Increased blood pressure activates the baroreceptor reflex. 3. Baroreceptor reflex detects elevated blood pressure and sends signals to the brain. 4. The brain then signals the heart to slow down, thus normalizing the rapid heart rate in PSVT. Summary: A: Blocking beta-receptors would have the opposite effect, as beta-blockers slow down the heart rate. B: Stimulating norepinephrine release would increase heart rate, not slow it down. D: ACh esterase is involved in the breakdown of acetylcholine, not relevant to the mechanism of action of phenylephrine in PSVT.

Correct Answer: A

Rationale: Rationale: Atropine is the correct answer as it is an anticholinergic agent like propantheline, both inhibiting acetylcholine activity. This action reduces gastric acid secretion, aiding in peptic ulcer treatment. Neostigmine (B) increases acetylcholine activity, opposite to propantheline's effect. Propranolol (C) is a beta-blocker, not directly affecting gastric acid secretion. Phentolamine (D) is an alpha-blocker, also not related to reducing gastric acid secretion.

Correct Answer: B

Rationale: The correct answer is B: Only some bacteria will be killed by some antibiotics. Antibiotic resistance refers to the ability of bacteria to survive and grow despite the presence of an antibiotic. This occurs when bacteria evolve and develop mechanisms to defend against antibiotics. It is not accurate to say that no bacteria will be killed by any antibiotic (choice A) as some bacteria may still be susceptible to certain antibiotics. Antibiotics are not effective against viruses, so choice C and D are incorrect. In summary, antibiotic resistance specifically pertains to bacteria developing the ability to survive some antibiotics, making choice B the correct answer.

Correct Answer: B

Rationale: The correct answer is B: neutralisation, yellow. In a neutralization reaction between an acid and a base, the acidic and basic properties neutralize each other, resulting in a salt and water. The indicator phenolphthalein is commonly used in acid-base titrations, turning pink in basic solutions and colorless in acidic solutions. When the reaction is complete and the solution is neutral (pH 7), phenolphthalein appears yellow. Therefore, the color of the mixture at the end of a neutralization reaction is yellow. Choices A, C, and D are incorrect because neutralization reactions typically result in a yellow color, not orange, and redox reactions do not involve the same color changes as neutralization reactions.