Isoprenaline produces the following actions EXCEPT:

Correct Answer: D

Rationale: Step-by-step rationale: 1. Isoprenaline is a beta-adrenergic agonist. 2. It directly stimulates beta adrenoceptors, leading to effects like increased heart rate. 3. Isoprenaline causes bronchodilation by relaxing bronchial smooth muscles. 4. It also causes vasodilation, leading to decreased blood pressure. 5. Isoprenaline does not have a direct effect on intestinal motility, making option D incorrect. Summary: Option D is incorrect as isoprenaline does not increase intestinal motility. Options A, B, and C are correct as isoprenaline directly stimulates beta adrenoceptors, relaxes bronchial smooth muscles, and decreases blood pressure, respectively.

Correct Answer: D

Rationale: The correct answer is D because X, a mixture of amphetamines, works by releasing neuronal noradrenaline, causing excessive sympathetic effects like severe rises in blood pressure. This is how the drug helps manage ADHD symptoms. The other choices are incorrect because A (blocking muscarinic receptors) would not be related to the autonomic effects seen with X, B (blocking β2 receptors) would not explain the fatal autonomic effects, and C (inhibiting MAO) would not lead to the described autonomic effects. Therefore, D is the correct choice based on how X works in the body to produce its effects on the sympathetic nervous system.

Correct Answer: B

Rationale: The correct answer is B: a length of DNA that codes for a protein. Genes are specific sequences of DNA that encode instructions for building proteins. This is the fundamental role of genes in the process of protein synthesis. Choice A is incorrect because not all DNA in a cell controls metabolic reactions; some DNA is non-coding. Choice C is incorrect as it refers to the entire nucleus and its contents, not just the gene. Choice D is incorrect as genes do not solely determine the inheritance of sex; they also code for other traits. In summary, the definition of a gene as a segment of DNA that codes for a protein aligns with the known function and role of genes in genetics and molecular biology.

Correct Answer: D

Rationale: Certainly! The correct answer is D because it includes statements 3 and 4, which are both true. Statement 3 is correct, as air pollutants can lead to various health issues. Statement 4 is also accurate, as air pollutants can contribute to environmental degradation. Statements 1 and 2 are incorrect as they are not included in the correct answer. Statement 1 may not be universally applicable, and statement 2 does not cover the broad impact of air pollutants on both health and the environment as indicated in statements 3 and 4. Therefore, choice D is the most accurate based on the information provided.

Correct Answer: D

Rationale: The correct answer is D: red supergiant → supernova → black hole. This sequence is part of the life cycle of a very large mass star. Red supergiants are massive stars in the later stages of their evolution. When a red supergiant goes supernova, it explodes in a massive stellar explosion, leaving behind a remnant that can collapse into a black hole due to the immense gravitational forces. Choices A and B are incorrect because planetary nebulae form from the outer layers of lower mass stars, not very large mass stars. Choice C is incorrect as neutron stars are more likely to form from the remnants of less massive stars.