The correct option is B Cephaleuros
Cephaleuros is a species of green algae. It is filamentous in structure and is a parasite of higher plants. It causes diseases called algal leaf spot, algal fruit spot and green scurf. This leads to an economic loss of the plant. Factors responsible for these algal infections are poor plant nutrition, poor soil drainage, and stagnant air. Thus the correct answer is option B.