下列不是达尔文自然选择学说中心内容的是（　　）

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!