翻译一句话：The object of the exercise was to prevent the public from seeing what they ought to see.

中文翻译 ：那个行动的目的是阻止/防止公众看见他们应该看到的东西

句子结构为:

主语:The object of the exercise 

系动词:was

表语:to prevent the public from seeing what they ought to see(不定式作表语,说明主语的具体内容)

prevent sb from doing sth阻止/防止某人做某事

My only idea was to prevent the woman from speaking. 

我唯一的想法就是不让那女人讲话。 

Cotton mittens will prevent the baby from scratching his own face. 

棉的连指手套使婴儿不会抓伤自己的脸。 

His prompt action prevented the fire from spreading. 

他的果断行动制止了火势的蔓延。 

I have been unavoidably prevented from coming. 

我身不由己, 不能前往。