完形填空

Sir Isaac Newton was a scientist who discovered the law of gravity （重力）. People have learned that Isaac Newton once 1 when he was thinking under an apple tree. 2 he was woken up by an apple falling on his head. He jumped up, shouting, "Gravity made the apple fall!"

Did the apple really fall on him? No one 3 for sure. The story of the apple may have some 4 but people who knew him have written that it never happened. Newton had actually been studying gravity and thinking about how apples fell down from a tree and not 5 for many years.