提出环保建议的表达 — 英语填空题
题目
学校的"节能小卫士"活动正在进行。请你根据句意，用 should 或 shouldn't 填空，完成下面三句环保建议，每空一词：
1. It's cold inside. We ___ close the windows to save energy.
2. There is no one in the classroom, so we ___ turn off the lights.
3. Don't leave the tap running when you brush your teeth. You ___ waste water.