1他们发现要掌握一门外语是困难的。 （find it difficult to）They find it difficult to learn a foreign language2这所学校平均每个班有45人。（on the average）Every class of this school has forty-five students on the average3请你把你要的东西清理出来并把其余的全扔掉。 （sort out）Please sort out all you want and throw away the rest4他被认为是我们当中跑得最快的人。（supposed to）He is supposed to ...
1 they find it difficult to master a foreign language.2 there are 45 students every class on the average in this school.3 please sort out things you need and throw the others....
