The most important part of testing urine with reagent strips is

Correct Answer: C

Rationale: The correct answer is C because the length of time the reagent strip is left dipped in urine affects the accuracy of the test results. Allowing the strip to stay in the urine for too long or too short a time can lead to incorrect readings. Option A is incorrect as it does not impact the testing process. Option B is also incorrect as expired strips may give inaccurate results. Option D is incorrect as the color of the urine does not determine the accuracy of the test, but rather the duration of exposure to the reagent strip.

Correct Answer: C

Rationale: The correct answer is C: Control pH levels. Blood helps maintain a stable pH level in the body by acting as a buffer system to prevent drastic changes in acidity or alkalinity. This is crucial for proper function of enzymes and other biochemical processes. Incorrect choices: A: Remove oxygen from the cells - This is incorrect as blood carries oxygen to cells, not removes it. B: Control blood vessel size - While blood vessels can regulate their size, it is not the primary function of blood. D: Increase body temperature - Blood does contribute to temperature regulation through circulation, but its primary role is not to increase body temperature.

Correct Answer: A

Rationale: The correct answer is A: Cartilage. Cartilage is the protective substance that covers the ends of bones. It acts as a cushion between bones, reducing friction and preventing wear and tear. Collagen is a protein found in connective tissues but is not the primary substance covering bone ends. Hormones and minerals do not directly protect the ends of bones.

Correct Answer: D

Rationale: Thyroid hormones, such as T3 and T4, are primarily responsible for regulating metabolism and growth in the body. They control how the body uses energy and help in the synthesis of proteins. Thyroid hormones do not directly influence heart rate and respiration (Choice A), bile production and potassium levels (Choice B), or kidney and liver function (Choice C). Thus, the correct answer is D as it aligns with the known functions of thyroid hormones.

Correct Answer: D

Rationale: The correct answer is D: Sharing a drug needle with an infected person. This is because HIV is transmitted through blood, and sharing needles can lead to direct blood-to-blood contact, increasing the risk of HIV transmission. Kissing on the cheek (A), shaking hands (B), and sharing utensils (C) do not involve direct blood contact, so the risk of HIV transmission through these methods is extremely low or non-existent.