Final answer:
The false statement about microtubule structure is that a-tubulin and B-tubulin are covalently bound.
Step-by-step explanation:
The false statement about the structure of microtubules is B) a-Tubulin and B-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
In reality, a-tubulin and B-tubulin do not covalently bind to form the tubulin dimer. Instead, they non-covalently associate with each other. The tubulin dimer then assembles into protofilaments, which come together to form the hollow structure of the microtubule.