材料一：我国某地地形简图。
材料二：A所在省份苹果产量全球第一，占全国的1/3和世界的1/8，苹果汁产量全球第一，占全国的84%和世界的1/3。
13－9＝____。
根据材料内容，选择正确答案。
There are 50 students in Class 8. Now they are doing a survey about how they spend their pocket money. Some spend it on books, and others spend it on visiting. What about you? Please read the form and answer the questions.
10%
55%
12%
13%
Buy some CDs and computer games.
Buy some snacks and drinks.
Buy some books in the bookshop.
Save it up and spend it traveling on holiday.
Buy some gifts for friends.
【提出问题】锌粒加入硫酸溶液反应生成的气体是什么？
【查阅资料】
①浓硫酸也可以与锌粒发生反应，但不会生成氢气，也不会生成氧气，能生成二氧化硫气体。
②二氧化硫有刺激性气味，易溶于水，能使品红（一种红色素）溶液褪色。
③浓硫酸有吸水性，常用作干燥剂
④氢氧化钠溶液可吸收二氧化硫，并生成亚硫酸钠（Na2SO3）和水
