—Why not come and join us in the game?—__________, but I must meet Mr. Smith at his office now.
Talk to your teacher and you will get help ________ you have a problem.
We have friends to help us fight against pollution, and trees are one of ________.
Now, people regard drinking tea ________ a culture more than a habit.
Our mother earth gives us ________ we need in our daily life.
Three bridges ________ over the river five years ago.