Teenagers should learn to protect (保护) ______from all kinds of dangers.
I happened to meet an old friend of __________ in the supermarket.
We live _______ a wonderful world _______ a lot of amazing things.
I had ______uncle. He said he saw ______UFO the other day.
--- This term, I plan to be the top student in our school. --- .
--- What’s in your bag? --- In it two books.