Question

A few protists possess structures to regulate their water content. They are
(a) membranes
(b) chromatophores
(c ) Nuclei
(d) contractile vacuoles

Answer 1

Hint: It is an osmoregulatory organelle of free-living amoebae and protozoa that controls the intracellular water balance by accumulating and expelling excess water out of the cell. This expulsion allows them to survive in the water under hypotonic stress.

Complete step-by-step answer:
Chromatophores are the organs that are present In the skin of many cephalopods, such as squids, cuttlefish, and octopuses, which contain pigment sacs that become more visible as small radial muscles open the sac and let the pigment expand under the skin. A membrane acts as a barrier that is selective due to which it allows some things to pass through it and some not. The things that can pass are molecules, ions, or other small particles. Membranes are of two types: synthetic and biological membranes. The nuclei are the nucleus that controls and regulates the activities of the cell and carries the genes, and structures that contain the hereditary information.contractile vacuole works like a pump to control the amount of water that comes into the cell by holding it inside the contractile vacuole until it enlarges and expands and it is full, it contracts and expels the excess water outside of the cell. So a contractile vacuole helps to regulate water content.

Hence the correct answer is option D.

Note: Nucleoli are the small bodies often seen with the nucleus. The gel-like matrix in which the nuclear components are suspended in the nucleoplasm. Protists lack a cell wall and thus soak up excess water from their surroundings and thus contractile vacuoles are crucial to drain them out.