Identify the trimester when each fetal development finding occurs. Select the appropriate trimester for each finding:

A. Formation of fingers, toes, and facial features Correct Trimester: 1st Trimester (Conception – 13 weeks) Explanation: By the end of the 1st trimester, organogenesis (organ formation) is largely complete. Weeks 7–8: Limb buds appear and begin differentiating into arms and legs. Weeks 9–12: Fingers, toes, facial features (eyes, nose, lips, ears) become clearly defined. This is a critical period for congenital malformations if exposed to teratogens. B. Fetus can hear and respond to external stimuli Correct Trimester: 2nd Trimester (14–26 weeks) Explanation: Around 18–20 weeks: The fetus develops the ability to hear sounds. External sounds can startle the fetus, and the heartbeat may change in response. Mother's voice and music can be recognized at this stage. C. Increase in body fat reserves Correct Trimester: 3rd Trimester (27–40 weeks) Explanation: In the final trimester, especially after week 32, fat accumulates under the skin. This provides energy and helps with temperature regulation after birth. The fetus also gains the most weight during this period. D. Brain develops most rapidly during this time Correct Trimester: 3rd Trimester (27–40 weeks) Explanation: Although brain development starts early, the most rapid growth occurs in the third trimester. There's a dramatic increase in brain volume, cortical folding, and neural connectivity. This trimester is essential for cognitive and motor development. E. Gender can be determined Correct Trimester: 2nd Trimester (14–26 weeks) Explanation: By week 18–20, an ultrasound can reliably show external genitalia. The sex organs begin forming in the 1st trimester, but become distinct and visible by the 2nd trimester. This is when many parents find out the baby's gender via an anatomy scan.