Final Answer:
Before removing the lock on the jack stand, you should be sure that the vehicle is supported entirely on the jack stand. Therefore, Option B is the correct choice.
Step-by-step explanation:
Ensuring that the vehicle is entirely supported on the jack stand is crucial for safety when working underneath a vehicle. Before removing the lock, the weight of the vehicle should be transferred and resting securely on the jack stand. This ensures stability and prevents any risk of the vehicle collapsing or shifting unexpectedly.
Option A, stating that there is no load on the jack stand, is incorrect as the load should be on the stand for support. Option C, mentioning having one hand free, is not a sufficient safety measure; the focus should be on proper support from the jack stand.
Option B is the answer.