There used to be a lot of trees.变为否定句

请问 There used to be a park. There used to be a clean river.为什么不是There used to have a clean river ______ plenty of water in this river.A.There used to being B.there used to beC.There is used to beingD.There was used to be -------- a small book store in thistown.( they used to be ,it used to have ,there used to be ,there used to have) There used to be a lot of pandas,_______ ______? there used to be a lot of manatees是什么意思 there used to be a reastrant here 与there used to be here a reastrant哪个对 there used to be a reastaurant here 与there used to be here a reastaurant哪个对 英语翻译There used to be a coffee shop next to your house,did't there?其中,used to 英语翻译There used to be a coffee shop next to your house,did't there? There [ ]a river in front of our houseA used to have B was used to C used to be D was used to being there used to be的意思!RT, there used to be a hospital near here 变否定句 there ___ ___ be a hospital near there There _______ a lot of trees in the park,weren't there?A use to be B used to be C used be There used to be a factory,wasn't there?这句话对吗? There used to be only school here,but now there are a few school. There used to ____(be) a theater here ,didn't there? there used to be a tall tree in front of the house.为什么要加be