Which of the following is the most important quarantine nematode pest of potato?

Correct option is D

The potato cyst nematode (Globodera rostochiensis) is one of the most serious quarantine pests of potatoes worldwide. It forms cysts in the soil and attacks potato roots, leading to yield losses up to 80%. Strict quarantine measures are required to prevent its spread.
Thus, the correct answer is (d) Cyst nematode (Globodera rostochiensis).