The correct answer is option D
The protists are the kingdom that has organism which neither lies in the category of animals nor in plants. These are different from plants and animals.
Stentor protists fall into the subgroup of the protozoan. They are single celled organisms but some of them can be seen through the naked eyes because of its size.
Some Stentor grows upto 0.6-2 milimeters in length. (600 micrometer-2000 micrometer).This is a unusual length of protozoans that can be seen without microscope else other protozoans cannot be seen without microscope.
