Members of the protista kingdom contain multi-celled organisms such as kelp and single-celled organisms such as .

The correct  answer will be Paramecium.

Explanation:

Protista is a heterogeneous group of simple eukaryotic organisms which did not arise from a single ancestral protist.

The members of protist are polyphyletic, which means they are not closely related to each other and do not share many common characters. They vary greatly in organization from single-celled to synctial to multi-cellular organisms.

The most common single-celled protista is Paramecium.

Paramecium are unicellular protist found in freshwater habitats, shaped like a sole of a shoe with short hairy structures on its body called cillia. Cillia helps in locomotion and dragging the food to its oral cavity.

Thus, Paramecium is the correct answer.