Correct Answer: D

Rationale: In patients with COPD, the respiratory drive is often stimulated by low oxygen levels. Administering too much oxygen can inhibit this hypoxic drive, leading to respiratory depression and potential respiratory failure. Therefore, it is crucial to carefully regulate the oxygen therapy to prevent the inhibition of the respiratory hypoxic stimulus in COPD patients.

Correct Answer: A

Rationale: Proper hand washing for 30 seconds is recommended after routine patient contact as it effectively removes pathogens. This duration ensures thorough cleaning without excessive time consumption, promoting infection control and prevention.

Correct Answer: B

Rationale: A positive guaiac test is used to detect the presence of occult (hidden) blood in the stool, suggesting bleeding from the gastrointestinal tract. It is a rapid screening test that can provide immediate information to the healthcare provider about possible gastrointestinal bleeding in patients presenting with symptoms such as nausea, vomiting, diarrhea, and severe abdominal pain.

Correct Answer: D

Rationale: The appropriate needle size for insulin injection is 25G, 5/8" long. This size allows for accurate and comfortable insulin administration in subcutaneous tissue.

Correct Answer: D

Rationale: As individuals age, various changes occur in the vascular system. These changes include increased peripheral resistance of the blood vessels, decreased blood flow, and an increased workload of the left ventricle. Therefore, all the listed changes result from aging, making option D, 'All of the above,' the correct answer.