Everyone knows that ______ is dangerous to play with fire, but ______ is difficult is to prevent children from playing with fire.
English is taught _________ a foreign language in almost all school in China.
He asked ______ they would hold the meeting _____ it rained the next day.
Would you please _______ fill the same bottle _______ full?
Don't rush. There's still ______ time left.
-----Do you know if the old man is still living? ----- I'm sorry. He _________. He ______ for two months.