[观察例句]
1．Knowing where the ball would go wasn't easy.
2．Shooting with great accuracy was another thing he learnt.
3．In this way，practising day in and day out helped Stephen sharpen his skills.
[归纳用法]
1．v.ing形式作主语表示抽象的经常性的意义。
Reading aloud is very important for us to learn a foreign language.
大声朗读对我们学习一门外语是很重要的。
Going to bed early and getting up early is considered to be a good habit.
早睡早起被认为是一种好习惯。
2．v.ing形式作主语时常后置，此时须用it作形式主语，用形容词或名词作表语，但这类形容词和名词较少，常见的形容词有：enjoyable，good，hard，worthwhile，nice，useless，worth等。常见的名词或名词短语有：no use，no good，fun，hard work，a hard/difficult job，a wonder，a waste of time等。
