Final answer:
A single cilium contains a core of stable microtubules in a 9+2 array structure.
Step-by-step explanation:
A single cilium contains a core of stable microtubules arranged in a structure called a "9 + 2 array". This structure consists of a ring of nine microtubule doublets surrounding a single microtubule doublet in the center. The microtubules provide stability and support to the cilium, allowing it to carry out its functions.