What is a sign that the rear tire has gone flat?

Answer: C — The back of the motorcycle sways from side to side

When the rear tire of a motorcycle has gone flat, one of the most noticeable signs is that the back of the motorcycle sways from side to side. This occurs because a flat rear tire loses its ability to maintain proper contact with the road surface. As the tire deflates, it becomes unstable, which can affect the overall balance of the motorcycle. Riders may feel the rear end wobbling or swaying, making it difficult to control the bike, especially during turns. The other signs listed, while they may indicate issues with the motorcycle, are not specific indicators of a flat rear tire. A sudden loss of speed could be caused by various mechanical problems or engine issues, and a low front end might suggest other handling or suspension problems. Engine sputtering is typically related to fuel or mechanical failure, rather than the condition of the tires.