Which respiratory development begins by month 6?

• A. Lungs start producing surfactant
• B. Lungs are fully mature
• C. Breathing begins in utero
• D. The diaphragm stops moving

Answer: (A)

The main idea here is timing of fetal lung development, specifically when surfactant starts to appear. By about month six of gestation, the lungs begin producing surfactant, a fatty substance that coats the alveoli and lowers surface tension. This makes air sacs easier to keep open after birth and is crucial for successful breathing once the baby is born. Surfactant production is a milestone that helps the lungs start to function at birth, even though full maturity continues later in pregnancy and after birth.

Breathing in the womb isn’t true air breathing—fetal movements can resemble breathing, but gas exchange isn’t happening until after birth. Lungs aren’t fully mature by month six; they continue developing and become capable of more extensive function later. The diaphragm keeps moving; it doesn’t stop, so that option doesn’t fit either.