Final answer:
At a Yield sign, you must slow down, stop if required, and yield to all other traffic before proceeding. Hence, the correct answer is option C.
Step-by-step explanation:
When approaching a Yield sign, the law requires you to slow down, stop if necessary, and yield right-of-way to all other traffic. This means that you should check for any oncoming vehicles, pedestrians, or cyclists, and give them the right to proceed before you enter. If the way is clear, you may proceed without a full stop, but you must be prepared to stop if the traffic conditions require it.