Microtubules have an inner diameter of and an outer diameter of . Microtubules have an inner diameter of and an outer diameter of . 15 mm; 25 mm 8 nm; 12 nm 25 nm; 30 nm 15 nm; 25 nm 7 mm; 14 mm

C. 25 nm; 30 nm

Explanation:

Microtubules are tubulin polymers which form part of the cytoskeleton and provide the eukaryotic cells with structure and shape. A microtubule's outer diameter is 30 nm, and its inner diameter is 25 nm.

Microtubules are fibrous, hollow shafts whose principal function is to support and shape the cell. They often serve a role of transport, as they are the routes by which organelles travel through the cell.

Hence, the correct option is C.