Correct Answer: D

Rationale: The correct answer is D because a loss of air conduction, known as conductive hearing loss, refers to a problem conducting sound waves through the outer or middle ear. This type of hearing loss can be caused by issues such as earwax buildup, fluid in the middle ear, or problems with the ear canal or eardrum. Choices A, B, and C are incorrect because air conduction is not the most efficient pathway for hearing (choice A), it is not caused by vibrations of bones in the skull (choice B), and the pitch of sound is determined by the frequency, not the amplitude (choice C). Conductive hearing loss specifically relates to the transmission of sound through the outer and middle ear structures, making choice D the correct statement.

Correct Answer: A

Rationale: The correct answer is A: At birth, the head is one fifth the total length. This is because newborns have relatively larger heads compared to their body size. This is known as cephalocaudal growth, where development starts from the head and progresses down the body. The head being one-fifth of the total length is a normal proportion in newborns. Choice B is incorrect because at birth, the chest circumference is usually greater than the head circumference. Choice C is incorrect as the head size reaches about 80% of its final size by age 2, not 3 years old. Choice D is incorrect because the closure of the anterior fontanelle at 2 months does not necessarily mean the head will appear proportionate to the body; it continues to grow in proportion to the body size.

Correct Answer: A

Rationale: The correct answer is A: acquired immunodeficiency syndrome (AIDS). The dark red confluent macule on the hard palate is known as Kaposi's sarcoma, a common manifestation of AIDS. This lesion is caused by Human Herpesvirus 8 and is often seen in patients with compromised immune systems. Measles (B) typically presents with a rash, not a dark red macule. Leukemia (C) does not typically manifest as a dark red macule in the mouth. Carcinoma (D) refers to cancer and would present differently than Kaposi's sarcoma. In summary, the presence of a dark red confluent macule on the hard palate in a patient with a history of intravenous drug abuse is highly suggestive of AIDS, specifically Kaposi's sarcoma.

Correct Answer: C

Rationale: The correct answer is C because the normal eardrum of a newborn can appear thick and opaque due to the presence of vernix or desquamated epithelium. Immobility of the drum (Choice A) is not a normal finding in a newborn and could indicate a problem. An "injected" membrane (Choice B) would suggest inflammation or infection, not necessarily infection. The appearance of the membrane in a newborn is not identical to that of an adult (Choice D) as it may have a different color, thickness, or opacity due to developmental differences.

Correct Answer: D

Rationale: The correct answer is D because it directly addresses the concern of a possible perforated eardrum by inquiring about the relationship between ear pain and discharge. This is crucial in assessing the severity of the condition. Choice A is incorrect as it focuses on subjective symptoms not specific to a perforated eardrum. Choice B is irrelevant as it doesn't pertain to the immediate concern. Choice C is also incorrect as it doesn't target the current issue of a potential perforated eardrum. Asking about ear pain and discharge helps determine the likelihood of a perforated eardrum and guides further assessment and care.