The best way to explore _______ countryside is on _______foot.
With the development of science, more new technology__________ to the fields of IT.
Some can never go above 4000 meters, because their body is unable to ___________ these extreme conditions.
I feel it is your husband who __________ for the spoiled child.
I hear that Mrs. Lin has been ________ with the translation of a French novel these months.
Mary opened the door. There______ she had never seen before.