Final answer:
The answer to the student's question is A) outer doublets; central pair, reflecting the typical "9 + 2" microtubule pattern found in eukaryotic flagella and cilia.
Step-by-step explanation:
The axonemal "9 + 2" pattern of microtubules is nine outer doublets surrounding a central pair. The correct answer to this question is A) outer doublets; central pair. This structural arrangement is a characteristic feature of eukaryotic flagella and cilia, where a ring of nine microtubule doublets surrounds two central microtubules, forming the "9 + 2 array". These structures arise from a basal body, which is similar to centrioles and organized as a ring of nine microtubule triplets. The basal body serves as the nucleation point for the formation of ciliary or flagellar axonemes that are surrounded by plasma membrane and display the distinct 9 + 2 microtubule array in cross sections as seen by electron micrographs.