You Are Sitting in Lecture and You Decide to Leave

You are sitting in lecture and you decide to leave the room for a minute.When you return,the professor is describing a cytoskeletal component and states that these fibres are thin and consist of two rows of protein subunits wound around each other in a long spiral.Since you left the room,you did not hear which cytoskeletal component is being referred to,but,since you read the book before you came to class,you know that it is

A) the microtubules.
B) the intermediate filaments.
C) microfilaments.
D) none of the above.