Final answer:
Microtubule assembly can be initiated from the e) centrosome, which contains centrioles composed of microtubules. Hence, e) is correct.
Step-by-step explanation:
The assembly of microtubules can be initiated from the centrosome. The centrosome is a microtubule-organizing center found near the nucleus of animal cells.
It contains a pair of centrioles, each composed of nine triplets of microtubules. Microtubules in eukaryotic flagella and cilia also arise from a basal body, which is similar to centrioles.