Final answer:
When you're on third base with 1 out and the batter hits a fly ball to the left fielder, you should stay at third and tag up after the catch. This ensures a safe opportunity to run home if you can.
Step-by-step explanation:
When you're the runner on third base with 1 out and the batter hits a fly ball to the left fielder in baseball, you should stay at third base and tag up after the catch (option a). This means that you stay put at third base until the left fielder catches the ball, and then you can start running towards home plate if you think you can safely make it without being tagged out. This strategy is important because if the left fielder catches the ball and throws it to home plate before you can touch it, you will be out.