sentence: Knowing a clean and tidy city is no less appealing to the tourists than beautiful scenery and bargain shopping , both the authority and the citizens understand the need to keep our city clean in order to keep the tourists coming . Therefore , they are serious about protecting the environment .
modified: Knowing a clean and tidy city is no less appealing to the tourists than beautiful scenery and bargain shopping , both the authority and the citizens understand the need to keep our city clean in order to keep the tourists coming , therefore they are serious in protecting the environment .
transformation: PUNCT, PUNCT, PREP