I'll give you a question, please answer with step-by-step reasoning process.
Sally loved the color of fallen leaves in autumn. She often took long walks in September. Where might she walk?\nOptions:\n- roof\n- tree\n- ground\n- forest\n- fall season

forest
Person can walk in the forest.

Forest have many tress so it have many fallen Leaves in the season of autumn.

September comes in the autumn season.

.

Final answer: forest