American schools begin in September after a long summer holiday. There're two terms in a school year. The first term is from September to January, and the second term is from February to June. Most American children begin to go to school when they're five years old. Most students are seventeen or eighteen years old when they finish high school.
      High school students take only five or six subjects each term. They usually go to the same classes every day, and they have homework for every class. After class, they do a lot of interesting things.
     After high school, many students go to college(大学). They usually have to pay a lot of money. So, many college students work after class to get money for their studies.

甲数是乙数的5倍，乙和甲的比是____∶____．

上个世纪，科学家希尔为了探究光合作用在哪里进行，曾经设计类似下图实验．把刚采摘的且生长旺盛的树叶捣碎，采用某种方法获得含有叶绿体的滤液，分成三等份．把其中两份直接放入A，B培养皿，第三份除去叶绿体后放入C培养皿．将三个培养皿置于同一地点，A，C培养皿接受光照，B培养皿遮光处理．一段时间后，观察到A培养皿中产生气泡，其中的气体能使带火星的木条复燃；B，C培养皿中未产生气泡．结合所学知识，分析判断下列叙述，其中不正确的是（　　）