The first sign of sexual development in males is typically the:

Rationale:
A. A partially vaccinated 4-year-old is at highest risk for pertussis because incomplete vaccination provides suboptimal immunity, leaving the child vulnerable to infection.
B. An infant born at term may have some passive maternal antibodies if the mother was vaccinated, offering partial protection.
C. A child who came in contact with an infected person is at risk, but the degree of susceptibility depends on immunity status. A fully vaccinated child has significantly lower risk.
D. A newborn whose mother received DTaP in the third trimester typically has transplacental antibodies, providing temporary protection during the first few months of life.

Rationale:
A. Headaches and breast tenderness are more commonly associated with premenstrual syndrome (PMS) rather than dysmenorrhea.
B. Nausea, vomiting, and back pain are classic findings of dysmenorrhea, which is painful menstruation often caused by increased prostaglandin production leading to uterine contractions and associated systemic symptoms.
C. Urinary frequency and burning suggest a urinary tract infection rather than menstrual pain.
D. Vaginal dryness and pruritus are signs of irritation or hormonal changes, not dysmenorrhea.