The nurse practitioner is providing anticipatory guidance to the caregiver of a child with cystic fibrosis. The most appropriate advice about dietary management should include:

Rationale:
A. Withdrawal from physical activity such as track is not necessary for a healthy, uncomplicated pregnancy; regular exercise is encouraged.
B. Limiting sexual intercourse is not routinely required in a normal pregnancy unless there are complications.
C. Avoiding undercooked steaks and other undercooked meats is important to reduce the risk of foodborne infections, particularly Toxoplasma gondii and other pathogens, which can be harmful to the developing fetus.
D. Weight gain should not be limited to 15 pounds; recommendations vary based on pre-pregnancy BMI, and restricting weight gain unnecessarily may be harmful.

Rationale:
A. The appearance of downy pubic hair occurs after the initial signs of puberty and typically represents Tanner stage 2–3 development.
B. Enlargement and lengthening of the penis usually occur after testicular enlargement, often a few months later, as puberty progresses.
C. Axillary and facial hair develop in later stages of puberty and are not initial indicators of sexual maturation in males.
D. Enlargement of the testicles and scrotum is the first and most reliable sign of puberty in males, generally occurring between ages 9 and 14. Testicular growth reflects activation of the hypothalamic-pituitary-gonadal axis, leading to increased testosterone production and the subsequent development of secondary sexual characteristics. Monitoring testicular size is therefore a key component in assessing the onset and progression of male puberty.