Cilia and flagella are most similar in

a. length
b. the kinds of cells that have them
c. their internal composition and structure
d. their location along the cell's periphery
e. the number that cells usually have

The answer is c. Their internal composition and structure.

Explanation:

Cilia and flagella are both composed of microtubules. Two microtubules combine to form a doublet. Cilia and flagella both contain 9 such doublets, corresponding to the 9+2 microtubule arrangement.Cilia and flagella are both covered by the projections of the cell membrane.

Eliminating Other Options:

a. Cilia and flagella are differentiated principally on the basis of length. Cilia are only a few microns long whereas flagella can be as long as 2mm.b. Cilia and flagella cannot be compose of cells as they themselves help cells to locomote. Cilia and flagella are organelles made up of microtubules which are linear polymers of the protein, tubulin.d. Cilia are located all over the cell whereas flagella are present on specific end, as they act like a propeller or motor.e.Different cells have varied amounts of cilia and flagella.