情态动词must表达必须遵守的规则 — 英语填空题

Mr Green 在操场边贴出新规则，内容包括：使用单杠前 must wear sports shoes（必须穿运动鞋），恶劣天气时 mustn't play on it（禁止玩耍）。请根据句意用 must 或 mustn't 填空（每空一词）。Today the sun is shining, so the students ___ follow the rule and wear sports shoes before playing on the bars. On rainy days, they ___ play on the bars.