The correct option is(4) having two types of nuclei
Explanation:
Ciliates differ from all other protozoans in having two types of nuclei.
These two nuclei are usually of different size, i.e. one is meganucleus and the other is micronucleus. The former controls metabolism whereas the latter is concerned with reproductions, e.g. paramecium.
In other protozoans, like Amoeba, single nucleus is present which is involved in metabolism and reproduction.
Other options are incorrect because Ciliates use filter feeding mechanism for obtaining food.
Like other protozoans, they also possess contractile vacuoles.
Ciliates use cilia for locomotion.
