Whenever I met her，________ was fairly often，she greeted me with a sweet smile.

12. The teacher didn’t _____ to myquestions which were not too difficult for me to think over.

Is the book Lock And Key in the library? — _____. The school has just bought many new books. [ ]

What’s the _____ of the car at present— It’s about 70 kilometers an hour.

The math problem is _____ difficult that only _____students can work it out.