提出建议：Let's... / We should... — 英语填空题
题目
环保小卫士 Lily 在写绿色倡议书。请从括号中选择所给词的正确形式填空，每空一词（注意句型要求）。1. Let's ______ (walking) to school together tomorrow. 2. We should ______ (throwing) rubbish into the bin, not on the ground. 3. Let's ______ (planting) more trees to make our city green. 4. We should ______ (saves) water every day.