The correct option is
B Sexually dimorphic
Ascaris lumbricoides is elongated, cylindrical, and tapering at both ends. It is a large-sized nematode showing sexual dimorphism, i.e., sexes are separate. In females Ascaris, there is the genital pore or vulva; males do not have a separate genital pore.
So, the correct answer is 'Sexually dimorphic'.