Correct Answer: C

Rationale: Precipitous is best defined as being swift, meaning sudden, rapid, or happening quickly. It is often used to describe a steep and very steep drop or rise. The word does not refer to being damp, gentle, or dull. 'Damp' means slightly wet, 'gentle' means mild or moderate, and 'dull' means lacking interest or excitement.

Correct Answer: D

Rationale: Urea is the correct answer. It is the crystalline compound formed in the liver from the breakdown of proteins, a byproduct of protein metabolism. Urea is excreted by the kidneys in the form of urine, aiding in the elimination of nitrogenous waste from the body. Uracil (Choice A) is a nitrogenous base found in RNA, not a product of protein metabolism. Urine (Choice B) is the liquid waste excreted by the kidneys but not the crystalline compound resulting from protein metabolism. Ureter (Choice C) is a duct that carries urine from the kidneys to the bladder, not the compound produced from protein metabolism.

Correct Answer: A

Rationale: The correct answer is A: "convulsion." A paroxysm is defined as a sudden spasm or convulsion. The word "convulsion" specifically refers to a violent and involuntary contraction or spasm of muscles, which aligns perfectly with the description of a paroxysm. On the other hand, choices B, C, and D are incorrect. "Symptom" (B) refers to a manifestation of a condition rather than a physical spasm. "Efficacy" (C) relates to effectiveness or success, not a sudden spasm. "Embolism" (D) refers to the obstruction of a blood vessel, which is unrelated to the concept of a sudden spasm. Therefore, convulsion is the most suitable synonym for a paroxysm in this context.

Correct Answer: D

Rationale: The correct answer is D, 'Scar.' A cicatrix is a scar, which is a mark left on the skin or within body tissue after the healing of a wound or injury. Choices A, B, and C ('Beetle,' 'Scalpel,' and 'Antidote') are incorrect as they do not represent synonyms for cicatrix.

Correct Answer: B

Rationale: The correct answer is B: A type of lipoprotein. LDL stands for Low-density lipoprotein, which is a type of lipoprotein that carries cholesterol through the bloodstream. LDL is often referred to as 'bad' cholesterol because high levels of LDL can lead to plaque buildup in the arteries, increasing the risk of heart disease and stroke. Choices A, C, and D are incorrect as they do not accurately describe the abbreviation LDL.