The correct option is C Louse
Louse is the wingless insect. They belong to the order Phthiraptera and class Pterygota. These are obligate parasites. They live on the bodies of warm blooded animals. They feed on the blood of the host. Arachnida is a group of organisms which have jointed legs. These are invertebrates animals or arthropods. This group includes the spiders, scorpions, etc.
Thus, the correct answer is option C.