祈使句表达建议与劝告 — 英语选择题

班会讨论如何让校园更环保，老师请大家判断哪条标语正确地用祈使句提出了劝告。下列句子中符合祈使句表达建议与劝告规范且无语法错误的一项是（　　） A. Don't to waste water when you wash your hands. B. Please turn off the lights when you leave the classroom. C. Let's not to pick flowers in the school garden. D. Doesn't throw litter everywhere on the playground.