The Great Green Wall will stop the wind _________ the earth away. [ ]

I don’t think one can keep healthy _____ taking enough exercise.[ ]

When ______ comes to research into heart disease and its effects on the body, we do not have adequate substitutes for the use of animals.

Last month I travelled across the Sahara Desert bycamel with some locals. Whatamazing experience!

Why are you so frustrated, Ben? —I was late for class again. I’m afraid Miss Li will be _________ me.