Final answer:
At 20 weeks' gestation, the fundal height is at the level of the umbilicus and the fetus's size and weight could be likened to that of a banana.
Step-by-step explanation:
At 20 weeks' gestation, the correct answer is: A. At the umbilicus; a banana. During the second trimester of pregnancy, which includes the 20th week, the fetus has grown substantially and the mother's uterus has expanded up to the point where the fundal height—the distance from the pubic bone to the top of the uterus—is generally at the level of the umbilicus, or belly button. The fetus at this stage would relatively weigh like a banana, indicating its size and weight progress.
In terms of fetal development, by 20 weeks the fetus is typically about 30 cm (12 inches) long. The placenta, now fully operational, supports the fetus, providing nutrition and waste elimination, as well as hormones necessary for the pregnancy. The significant growth of the fetus continues into the third trimester, where the baby prepares for its final development stages before birth.