Final answer:
Lanugo is a fine hair that covers the fetus's body until close to the time of birth, typically around weeks 17-20 of gestation.
Step-by-step explanation:
Lanugo is a fine, colorless hair that covers a fetus's face and body until it is shed close to the time of birth.
According to the given information, during weeks 17-20 of gestation, the fetus is covered with lanugo. However, it is important to note that extremely premature infants might still display residual lanugo.