Final answer:
The microtubule typically depolymerizes when GTP hydrolysis occurs on a tubulin molecule at the plus end before another tubulin molecule is added.
Step-by-step explanation:
If GTP hydrolysis occurs on a tubulin molecule at the plus end of a microtubule protofilament before another tubulin molecule is added, the microtubule typically depolymerizes (Option B). This happens because GTP hydrolysis on tubulin reduces the binding strength between the tubulin dimers, leading to the instability of the microtubule structure at the plus end. As a result, the microtubule tends to lose its dimers, causing it to shrink in size. This dynamic instability is a fundamental property of microtubules, allowing for rapid reorganization within the cell and is critical for many cellular processes, such as cell division and intracellular transport.