What covers the entire body of the fetus around 24 weeks gestation?

The correct choice is that vernix and lanugo cover the entire body of the fetus around 24 weeks gestation. Vernix caseosa is a greasy, protective coating that appears on the skin of the fetus, serving to protect it from the amniotic fluid and prevent skin maceration. Lanugo is fine, soft hair that also develops around the fetus, providing an insulating layer and further protecting the skin. Around the 24-week mark, both of these substances become more prominent and start to cover the fetus's body.

Chorion, amniotic fluid, and placenta serve different roles in fetal development. The chorion is the outer fetal membrane contributing to the formation of the placenta, rather than a covering for the fetus itself. Amniotic fluid, while crucial for cushioning and fetal movement, is a liquid and does not provide a surface covering like vernix and lanugo. The placenta is an organ that facilitates nutrient and gas exchange but does not directly cover the fetus.