The most important part of testing urine with reagent strips is

Correct Answer: C

Rationale: The correct answer is C: The length of time the reagent strip is left dipped in the urine. This is crucial because the reaction between the urine components and the reagent on the strip needs a specific amount of time to occur accurately. If the strip is not left in the urine for the correct duration, the results may be inaccurate. A: Touching the reagent bottle with the strip when reading is incorrect because it does not impact the accuracy of the test results. B: Using strips that have not expired is important, but not the most critical factor in the testing process. D: The color of the urine when testing it is also not as important as the duration of time the strip is dipped in the urine for accurate results.

Correct Answer: C

Rationale: The correct answer is C: Control pH levels. Blood helps maintain the body's pH balance within a specific range, typically around 7.4, which is crucial for proper bodily functions. It does this by acting as a buffer, regulating the concentration of acids and bases in the body. In contrast, choice A is incorrect because blood actually transports oxygen to cells. Choice B is incorrect as blood vessel size is mainly controlled by the nervous system and hormones. Lastly, choice D is incorrect as blood does not directly regulate body temperature, which is primarily controlled by the hypothalamus in the brain.

Correct Answer: A

Rationale: The correct answer is A: Cartilage. Cartilage is the protective substance that covers the ends of bones, providing cushioning and reducing friction during movement. It also helps in absorbing shock and maintaining joint flexibility. Collagen (B) is a protein found in connective tissues but not the primary substance covering bone ends. Hormones (C) are signaling molecules that regulate various bodily functions, not related to bone protection. Minera (D) is a misspelling and not a relevant substance for bone protection.

Correct Answer: D

Rationale: The correct answer is D: Metabolism and growth. Thyroid hormones, such as T3 and T4, play a crucial role in regulating metabolism by influencing the body's energy production and consumption. They also help in the growth and development of various tissues and organs. This is supported by scientific research and physiological understanding. Explanation for other choices: A: Heart rate and respiration - While thyroid hormones can indirectly influence heart rate and respiration through their effects on metabolism, they are not the primary regulators of these functions. B: Bile production and potassium - Thyroid hormones do not have a direct role in regulating bile production or potassium levels in the body. C: Kidney and liver function - While thyroid hormones can affect kidney and liver function to some extent, their primary role lies in metabolism and growth regulation.

Correct Answer: D

Rationale: The correct answer is D, sharing a drug needle with an infected person. HIV can be transmitted through blood-to-blood contact, and sharing needles can lead to direct exchange of infected blood. Kissing, shaking hands, or sharing utensils do not involve direct blood contact, making them unlikely modes of HIV transmission.