Correct Answer: A

Rationale: The correct answer is A: 'There is an extra chromosome on the 21st pair.' Down syndrome is caused by the presence of an extra copy of chromosome 21, known as trisomy 21. This additional genetic material leads to the characteristics associated with Down syndrome. Choices B, C, and D are incorrect because Down syndrome is not due to a missing chromosome or having two pairs of the 21st chromosome; it results from the presence of an extra chromosome on the 21st pair.

Correct Answer: D

Rationale: A Mantoux tuberculosis skin test without induration is considered negative. In this case, with 5mm of erythema and no induration, the result is negative, indicating no current infection. The best initial nursing action is to document these negative results in the healthcare worker's medical record. Reviewing the history for possible exposure to TB is unnecessary as the test result is negative. Instructing the healthcare worker to return for a repeat test or referring for INH therapy is not warranted when the test is negative.

Correct Answer: D

Rationale: Referral for a skin biopsy is necessary to rule out potential malignancy of irregular skin lesions. Applying a topical antibiotic ointment (Choice A) is not indicated for irregular pigmented lesions. Monitoring the lesions for changes (Choice B) may delay appropriate intervention if malignancy is present. Advising the client to use sunscreen (Choice C) is important for sun protection but is not the priority when irregular lesions are present.

Correct Answer: D

Rationale: Instructing the client in the use of the PCA pump is the best initial nursing action for managing severe incisional pain after knee replacement surgery. The PCA pump allows the client to self-administer pain medication effectively, promoting better pain management. Administering a sedative may mask the pain temporarily but doesn't address the root cause. Repositioning the client for comfort or applying ice packs may provide some relief but doesn't address the need for effective pain control as the PCA pump does.

Correct Answer: B

Rationale: The correct answer is B: Recurrent spasms of the airways accompanied by edema and mucus production. Asthma is characterized by bronchospasms, inflammation, swelling of the airways, and increased mucus production. This leads to airway constriction, making it difficult to breathe. Choices A, C, and D do not represent the typical pathology seen in asthma. Chronic dilation and inflammation of the bronchi (Choice A) is more characteristic of bronchiectasis, progressive loss of lung function due to destruction of alveolar walls (Choice C) is seen in conditions like emphysema, and infection of the lung parenchyma (Choice D) is more related to conditions like pneumonia.