Final answer:
Motile cilia and flagella have a 9 + 2 microtubule arrangement, while non-motile primary cilia have a 9 + 0 arrangement, both crucial for their respective functions.
Step-by-step explanation:
The arrangement of microtubules in motile cilia and flagella is both described as a "9 + 2 array" arrangement due to the structure composed of a ring of nine microtubule doublets that surround a pair of microtubules in the center. This 9 + 2 arrangement is essential for the motility functions of these organelles, allowing flagella to propel cells with wave-like motion and cilia to beat back and forth. In contrast, a non-motile, primary cilium has a "9 + 0 arrangement", which means that it has the nine outer microtubule doublets but lacks the central pair present in motile cilia and flagella.