在下面数的 里填一个数字，使这个数是3的倍数．

39 , 里可以填：____

氯化钠是我们日常生活的必需品，也是重要的化工原料，可以制备一系列物质。氯化钠的用途如图所示，下列说法错误的是（ ）

【历史——选修4：中外历史人物评说】

材料：李自成，原名鸿基，明末农民起义领袖。参加农民起义以来，李自成在各地流动作战，并无固定的据点和严密的组织，也没有提出过明确的战斗目标。他在河南聚众获胜后，军中文士牛金星与李岩向李自成献策，提出均田免粮的战斗口号。均田免粮这一朴素的口号，恰好反映了农民群众的迫切愿望，从而产生了巨大的政治影响，极大地便利了农民军的发展。李自成还提出农民军平买平卖的口号。1644年在西安建立大顺政权，不久攻占北京，取代明朝而处于四面受敌的被动地位。特别是北面的清国和江南的明室残余，构成了夹击大顺的严重形势。北京城内的大顺政权正忙于筹备李自成做皇帝的登基大典，军士们则竞相追赃积财，准备还乡。大顺强敌压境，而军心涣散，失败不可免了。

——整理自《中国通史》等

根据短文理解，选择正确答案。

Letter One

Dear Editor,

    After I finish my homework, I often go online and chat with my friends. Sometimes I play Internet games. But my parents hate to see me playing games on the computer. Maybe they have heard too much news about how QQ and Internet games harm children. Once I went to a net bar to play games after school. But after that I told my parents that I was playing basketball at school. I said so because I didn't want to make them unhappy. I feel bad about it. However, I need to rest for a while by playing computer games after studying for a long time. I really want my parents to understand that. Do foreign parents do the same to their children? Please help me.

Li Ping, Nantong

Letter Two

Dear Li Ping,

    I think it's not strange for parents to keep their children away from anything bad. Foreign parents will do the same as your parents! They may not let their children watch TV for too long a time, or like your parents, they don't want their children to play computer games.

    Talk to your parents and be honest to them, I think. Tell them what you are doing and why you are doing so to make them understand you. It's never good to do things behind your parents' backs. They aren't fools as you think sometimes! Our parents seem to know what is the best for us. Remember: to be honest is the best way.

Good luck,

Rebecca