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：在缺词处加一个漏词符号（∧），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：在错的词下画一横线，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仅限一词；
2）只允许修改10处，多者（从第11处起）不计分。
Dear Harry,
I have good news for you that there will be a international music camp in our city this summer The camp is openly to students from all over the world who is interested in playing musical instruments. I know you are a music lover, so why not to join the camp together with us?
At the camp, campers are giving classes by experts in the moring and in the afternoon they do a couple of hour of practice. In the evening, there is a music exchange concert that campers can give performances and plays different kinds of music from their own counties.
I'm sure you will have a lot of funs there. I'm looking forward your reply.
Yours,
Li Hua
是反映家庭生活水平高低的重要指标。恩格尔系数减小，意味着（ ）