假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。
增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。
删除：把多余的词用斜线（＼）划掉。
修改：在错的词下划一横线，并在该词下面写出修改后的词。
注意：1）每处错误及其修改均限一词；
2）只允许修改10处，多者（从第11处起）不计分。
Last week, I take part in the Cultural Exchange Week. I enjoyed myself in England. I visited the city museum and several place of interest, which made me have better understanding of the English society, culture and history.
What's more, I was luckily enough to meet my pen friend Tom there. I stayed at his home. And I'll never forget the days when we spent together. When I left England, he offered to me a dictionary for a gift. It's of great help for me to learn English. I will make full use of them and learn English good.
I hope Tom will come to China when it's convenience for him!
HCO3﹣，使人体血液pH保持在7.35～7.45，否则就会发生酸中毒或碱中毒．其pH随c（HCO3﹣）：c（H2CO3）变化关系如下表：