91Ó°ÊÓ

Theprotists are the unicellular organisms, which are microscopic and exhibitdistinct modes of locomotion. They are motile and their locomotion helps them to survive viasensing their surroundings, feeding, and other features. The important mode of locomotion in protists is via the use of distinct structures like flagella, pseudopodia, and cilia.

A thin thread-like composition projecting from the cells, which assists in the locomotion of a cell is known as aflagellum. Apart from locomotion, they also possess a sensory function. They arelonger than cilia.

The extensions of the membrane, which allow a cell to move, and to engulf food particles are known aspseudopodia. Pseudopodia is also not the shortest organ of locomotion.

Thepellicle is a thin layer, whichcovers the membrane of the cell and provides support to the membrane, it is not a locomotory organ.

Thus, the optionsa, c, and d are incorrect.

The slender structures, which project from the cell body, and works in locomotion are known ascilia. They are shorter than flagella and are the shortest locomotory organs among the locomotory organs found in the protists.

Hence, the correct answer is option b.