环境问题已经成为制约社会发展和进步的严重问题。有下列几种说法：① 臭氧层的主要作用是吸收紫外线；② 温室效应将导致全球气候变暖；③ 酸雨主要是由于空气受到硫的氧化物和氮的氧化物污染所致；④光化学烟雾主要是有汽车排放的尾气引起的；其中正确的是（  ）

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。

    Guilin is in Guangxi Zhuang Autonomous Region, China, famous of its mountains and waters. I went here last summer and stayed for five day. During that time not only I enjoy the fascinating scenery like the unique mountains and clean rivers, but also I try the traditional weaving of Zhuang people. That impressed me most was the amazing folk-song-singing competition on the Li River, which attracted thousands of visitors or locals. Guilin enjoys a worldwide fame for it beautiful scenery, so it's well worth visiting. I am strongly recommend you to visit it. I believe you will have a wonderfully time.

小米公司正式成立2010年4月，是一家专注智能手机自主研发的移动互联网公司，定位于高性能发烧手机。小米手机、MIUI、米聊是小米公司旗下三大核心业务。“为发烧而生”是小米的产品理念。2013年底，实现含税销售额316亿元，然而其所有850个零配件均通过国内和国际市场销售。右图为其零部件供应厂方。读图回答下列问题。