考查动名词作主语.等于：
Working in these conditions is not a pleasure but a suffering.
同上.等于：
Eating this kind of food containing too much fat is no good.
英语中经常用动名词作主语,（表示泛指,如表示特指,常用不定式作主语）但在实际运用时,为了句子平衡,常用it作为形式主语,而把正真的主语放到句后.
it's no good/no use doing sth已成为一固定用法,意为：做某事是不好的/没用的.