Correct Answer: C

Rationale: At 5 months, infants typically can turn from their abdomen to their back. Rolling from back to abdomen and sitting erect without support occur later.

Correct Answer: B

Rationale: Physiologic anemia is caused by the transition from fetal to adult hemoglobin, with fetal hemoglobin having a shorter lifespan, leading to a temporary decrease in red blood cells.

Correct Answer: D

Rationale: The correct answer is D because at 9 months, infants become more mobile, increasing the risk of choking hazards from small objects left on the floor. Cautioning about putting the infant in a walker (Choice A) is not as crucial at this age as warning about choking hazards. While advising how to create a toddler-safe home (Choice B) is essential, the most critical concern at 9 months is small objects. Instructing on safety procedures during baths (Choice C) is important but does not address the immediate risk of choking hazards associated with small objects.

Correct Answer: A

Rationale: The first sign of puberty in boys is typically the enlargement of the testes. This is due to the increase in production of testosterone, which leads to physical changes such as growth of the testes. Choice B, decreased levels of testosterone, is incorrect as puberty is marked by an increase in testosterone levels. Choice C, voice deepening, and choice D, pubic hair growth, usually occur later in the puberty process compared to testicular enlargement, making them incorrect answers.

Correct Answer: B

Rationale: Hepatitis B vaccination should start at birth, and any child or adolescent not vaccinated should complete the series. Adolescents should receive three doses if they were not previously vaccinated.