20.—Though it is 30 years _____ we last met, I still remember the scene _____ we got separated on a rainy day.
--Hi, Jack! We’re going to have a walk along the beach this Sunday. --_______. I love sunshine.
________ the market in three months, the new product will make a big difference.
Mary _______ have arrived ten minutes earlier but her flight was held up because of the heavy fog.
________ you have learned should be made good use of ________ making mistakes in the coming college entrance exam.
I plan to move to the countryside as the air there is much fresher than________ in the city.