If someone's knees hurt after a one-week walking regimen, then Answer B is the answer I would give them - jogging in a swimming pool.
Wearing different shoes might be the solution for preventing a knee injury if shoes are proven to be a cause. But simply changing shoes and continuing to jog after an injury is not correct.
Instead, jogging in a swimming pool seems like the appropriate suggestion for someone who injures their knee on a running regime.
The water offers support by taking some of the weight off the knee and the joint, and yet still allows you to perform activities that build muscle around the knee, create more support in the long-run too.
Aqua-jogging is the term often used for jogging in a swimming pool, and it's an ever more popular fitness exercise, whether you have sustained a knee injury or not!