①取3支试管，编号注入2mL淀粉液；另取3支试管，编号各注入1mL新鲜的淀粉酶溶液

②将淀粉酶溶液注入相同温度下的淀粉液试管中，维持各自的温度5min

③向各试管滴一滴碘液

④将6支试管分成三组，每组各有一份淀粉液和一份淀粉酶溶液，分别放在60℃的热水、沸水和冰水中5min；

⑤观察实验现象．

阅读短文，下列问题

    People in many countries are learning English.Some of them are small children. Others are teenagers. Many are adults. Some learn at school, others learn by themselves. A few people learn English by hearing the language over the radio, on TV or in films. As we know, it's hard to learn a foreign language well. One must work hard to learn another language. Because we can't use it often. But if you have right ways to learn English, it's a piece of cake.

    Why do all these people want to learn English?It is difficult to answer this question. Many boys and girls learn English at school because it is one of their subjects required (要求) for study. They study their own language, math and English. Some people learn it because it is useful for their work. Many people learn English for their higher studies,because at colleges or universities some of their books are in English. Some people learn English because they want to read newspapers or magazines in English.

根据短文内容选择正确答案。