A new __________to teaching English, is being used here, and it has proven to be very helpful to the students. 

I didn’t have to work all weekend — I did it by _______. 

 —Shall we go out for a walk? —Sorry. This is not the right _________ to invite me. I am too tired to walk.

Antarctica holds 90% of the world’s ice, and most of its fresh water (70%) is in a frozen          .

I’ve listened to Professor Smith’s talk about medicine,but I still haven’t got a good understanding of its key _________.