must / mustn't 的用法 — 英语填空题
题目
看规则，先判断“该做”还是“不该做”，再用 must 或 mustn't 完成句子。Today is Sunday. Tom wants to cross the street, but the light is red. He ______ wait. When the light turns green, he ______ look left and right first. On the bus, he ______ eat ice cream, because it may make the bus dirty.（提示：依次填三空，用 must 或 mustn't）