Which of the following statements about the cytoskeleton is true?
a. all eukaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm
b. the cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell.
c. the three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another
d. actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end

c. the three cytoskeletal filaments perform distinct tasks in the cell

Explanation:

The cytoskeleton is composed by three main parts:

a. Microfilaments, that are polymers of actin. They act as tracks of the movement.

b. Microtubules, that are composed of tubulin. They are kind of cilia inside the cell to form so connection among organs.  

c. intermediate filaments, composed of different proteins. They maintain the cell with some flexibility.

All of them are in all the cytoskeletons of cells but they have different tasks.

Hope this info is useful.

b. lithosphere, asthenosphere, mesosphere   is the answer most likely