改错Therehavenotalawaysbeenpencils
There have not alaways been ncils and pens,rulers and books. Tousands years ago, no one knew about these things. 需要讲解
pencils 与 pens 之间的and 改为“，”并列成分之间都用“，”最后用and thousands 后加 of, 数字加 thousand后直接跟修饰成分，否则用thousands 但several等少数词除外 these改为those后者是承上，前者是启下，作用不同。题中是承上的用those