How many blood vessels are present in the umbilical cord?

Correct option is B

The umbilical cord contains two arteries and one vein. The two arteries carry deoxygenated blood from the fetus to the placenta, while the single vein carries oxygenated blood from the placenta back to the fetus.
Explanation of options: (a) ✘ Incorrect. The umbilical cord does not contain two veins. (b) ✔ Correct. The umbilical cord contains two arteries and one vein. (c) ✘ Incorrect. The umbilical cord does not contain two veins. (d) ✘ Incorrect. The umbilical cord has two arteries, not just one artery.