A.I. Explanation:

Option 1: "methods to improve your stamina quickly."

Explanation: The text mentions 'a few other tricks you can try to help you reach your goals faster,' which directly implies methods aimed at improving stamina quickly. This aligns with the overall theme of the passage, which focuses on enhancing fitness through walking.

Option 2: "suggestions on how to keep fit."

Explanation: While keeping fit is a general goal, the passage specifically refers to 'tricks' that help improve stamina quickly, not just general suggestions for fitness. This option lacks the specificity regarding stamina improvement.

Option 3: "benefits of different styles of walking."

Explanation: This option introduces a concept not mentioned in the text. The passage does not discuss different styles of walking or their benefits; it focuses on improving stamina through walking, making this option irrelevant.

Option 4: "different ways to build up your stamina over a long period."

Explanation: The passage emphasizes reaching goals faster, which contrasts with the idea of building stamina over a long period. This option misinterprets the intent of the 'tricks' as it suggests a slower approach rather than quick methods.