**Core Concept**
The umbilical cord is a vital structure connecting the fetus to the placenta, facilitating the exchange of oxygen, nutrients, and waste products. It contains two umbilical arteries and one umbilical vein, which are embedded in the Wharton's jelly, a gelatinous substance.

**Why the Correct Answer is Right**
The correct answer involves identifying the correct composition of the umbilical cord. The two umbilical arteries carry deoxygenated blood from the fetus to the placenta, where it is exchanged for oxygenated blood. The single umbilical vein carries oxygenated, nutrient-rich blood from the placenta to the fetus. The Wharton's jelly, a gelatinous substance, serves as a protective cushion for the blood vessels.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the umbilical cord does not contain a left and right ventricle, which are cardiac structures that pump blood in the heart.
* **Option B:** This option is incorrect because the umbilical cord does not contain a left and right atrium, which are cardiac structures that receive blood in the heart.
* **Option C:** This option is incorrect because the umbilical cord does not contain a pulmonary artery, which is a blood vessel that carries blood from the heart to the lungs.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the umbilical cord contains two umbilical arteries and one umbilical vein, which are embedded in the Wharton's jelly. This knowledge is crucial for understanding normal fetal development and identifying potential abnormalities in the umbilical cord.

**Correct Answer:** D. Two umbilical arteries and one umbilical vein, embedded in Wharton's jelly.