I didn’t quite follow him because he explained the theory _____that is too abstract for me.
With our knowledge _________ practice, we can make contributions to our society.
My sister_______ the League last month and she has decided to _______ the activity to help the aged next week.
Life would be happier if we could only be born at the age of eighty and ________reach eighteen.
You’d better get the second-hand car ________ before you sell it.
They believe that there is _________ in the world.