题目

   If you could change your child’s DNA in the future to protect them against diseases, would you? It could be possible because of technology known as CRISPR-Cas, or just CRISPR.   CRISPR involves a piece of RNA, a chemical messenger, designed to work on one part of DNA; it also uses an enzyme (酶) that can take unwanted genes out and put new ones in, according to The Economist. There are other ways of editing DNA, but CRISPR will do it very simply, quickly, and exactly. The uses of CRISPR could mean that cures are developed for everything from Alzheimer’s to cancer to HIV. By al正常环境中，呼出的气体和吸入的气体相比，其变化是（　　　）①温度升高　②水分增加　③氧气含量减少　④氧气含量增加　⑤二氧化碳含量增加A．①②③⑤B．①②④⑤C．①③④⑤D．②③④⑤