practising .
practice是名词,practise是动词.只有动词才能加ing.
need直接带动词原形时是情态动词.与其他情态动词一样,其否定形式是直接加not,其疑问形式是直接将need提到主语的前面.如：
肯定句：I need wear thick clothes.
否定句：I needn't wear thick clothes.
一般疑问句：Need I wear thick clothes?
肯定回答：Yes,you need.
否定回答：No,you needn't.
need后面接to do时是实义动词.其否定形式和疑问形式都要借助动词do.因为实义动词是不能像情态动词那样带not的,也不能像情态动词那样可以提到主语的前面.如：
肯定句：I need to wear thick clothes.
否定句：I don't need to wear thick clothes.
一般疑问句：Do I need to wear thick clothes?
肯定回答：Yes,you do.
否定回答：No,you don't.
但现在的口语中,实义动词need有这种用法：在否定句或疑问句中省略to.
如,上面的例子现在可以说成：
肯定句：I need to wear thick clothes.（在肯定句中,不变）
否定句：I don't need wear thick clothes.（在否定句中,可以省略to）
一般疑问句：Do I need wear thick clothes?（在疑问句中,可以省略to）
肯定回答：Yes,you do.
否定回答：No,you don't.