Which of the following is not a characteristic of a fetus at 36 weeks' gestation?

At 36 weeks' gestation, the characteristics of a fetus include several developmental milestones. The option stating that the fetus lacks hair and vernix is not accurate. In fact, by this stage of gestation, the fetus typically has both some amount of hair and vernix caseosa. Vernix is a protective coating that forms on the skin and helps to safeguard it from the amniotic fluid.

In contrast, the other characteristics mentioned are indeed typical for a fetus at this stage. The ability to respond to stimuli indicates that the nervous system is sufficiently developed, allowing for reactions to sound and light. The development of the heart chambers is essential for proper circulation, and at this point, all four chambers are generally fully formed. Additionally, the fetus accumulates body fat during the last trimester, which is crucial for thermoregulation after birth. Therefore, the correct answer highlights a misconception about fetal development at 36 weeks.