It was not until all the fish died in the river_____the villagers realized the serious pollution.
English has been very popular because it is the _______ language in many western countries.
---Do you know our home town at all? --- No, this is the first time I _____ here.
I can't _____ what you said because you spoke too quickly.
_______, China may have the largest number of English learners in the world.
Miss Gao asked her mother if she _______ to the hospital the day before when she was out.