Which one of the following statements about cilia is true?

Both flagella and cilia have a 9 + 2 arrangement of microtubules. This arrangement refers to the 9 fused pairs of microtubules on the outside of a cylinder, and the 2 unfused microtubules in the center Cilia contain an axoneme with ciliary dynein arms extending unidirectionally from one member of each doublet. Dynein "arms" attached to the microtubules serve as the molecular motors. Ciliary dynein has ATPase activity, and when it splits ATP, the adjacent doublets slide past one another and the cilium moves.