Millions of people all over the world use the word OK. In fact, some people say the word is used more often than any other word in the world. OK means all right or acceptable. It expresses agreement or approval.

        ____ Some people say it came from the Native American Indian tribe known as the Choctaw(乔克托语). The Choctaw word “okeh” means the same as the American word “okay”. Experts say early explorers in the American West spoke the Choctaw language in the nineteenth century.

        But many people doubt this. Language expert Allen Walker Read wrote about the word “OK” in reports published in the 1960s. He said the word began being used in the 1830s. ____ Some foreign­born people wrote “all correct” as “o­l­l­k­o­r­r­e­c­t”， and used the letters OK. Other people say a railroad worker named Obadiah Kelly invented the word long ago. They say he put the first letters of his name—O and K—on each object people gave him to send on the train.

        ____ The organization supported Martin Van Buren for president in 1840. They called their group the OK club. The letters were taken from the name of the town where Martin was born—Old Kinderhook, New York.

        Then there is the expression A­OK. It is a space­age expression. It was used in 1961 during the flight of astronaut Alan Shepard. He was the first American to be launched into space. His flight ended when his spacecraft landed in the ocean, as planned. Shepard reported, “Everything is A ­OK.” ____ One story says it was first used during the early days of the telephone to tell an operator that a message had been received.

        There are also funny ways to say okay. ____ These expressions were first used in the 1930s. Today, a character on the American television series The Simpsons says it another way. He says okely­doke.

A．Some people say okey­dokey or okey­doke.

B．Still others say a political organization invented the word.

C．Therefore, it has become popular in that area from then on.

D．But many experts don't agree on what the expression means.

E．Still, language experts do not agree about where the word came from.

F．It was a short way of writing a different spelling of the word “all correct”．

G．However, some experts say the expression did not begin with the space age.

已知函数y=（m+1）$x^{m^2-3}$ 是正比例函数，且图象在第二、四象限内，则m的值是（　　）

下列说法正确的组合是（  ）
①病毒是生命系统结构层次中最小单位
②德国的魏尔肖对施莱登和施旺的细胞学说的补充内容是：新细胞可以从老细胞中产生
③具有生命的结构都有蛋白质和核酸
④只能自己合成，不能从食物获取的氨基酸叫做必需氨基酸
⑤还原性糖和DNA的鉴定试验，都需要在沸水中水浴加热处理
⑥观察花生子叶中脂肪颗粒实验和观察根尖有丝分裂实验，都用到酒精，其作用是不一样的