Microtubules contribute to each of the following except a) mitotic spindles. b) filopodial structure. c) the human red blood cell disklike shape. d) orientation of plant cellulose microfibrils. e) intracellular transport.

Explanation:

The microtubules are made up of tubulin proteins and are hollow tubes that gives shape to the cell and organelle place in the cell. The movement of organelles occurs due to the transport function provided by the microtubules.  

Microtubules contribute to spindle apparatus involved at the time of cell division. The RBCs size is maintained by stiffness of microtubules. The microfibrils walls are arranged  parellely with cortical microtubules. The microtubules also function in intracellular transport of organelles and vesicles (membrane-bound). Thus, option b is correct.

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