问题 选择题

米饭是没有甜味的,但在口腔中却出现了甜味,原因是(  )

A.米饭中的糖类变成了氨基酸

B.米饭中的糖类变成了麦芽糖

C.米饭中的糖类变成了葡萄糖

D.米饭中的糖类变成了甘油

答案

A、米饭和馒头中含有淀粉,淀粉的分解产物不是氨基酸,所以该选项不符合题意;

B、唾液中含有淀粉酶,它是一种消化液,含有淀粉酶,将食物中的部分淀粉催化水解为麦芽糖,麦芽糖有甜味,所以该选项符合题意;

C、唾液中不含麦芽糖酶,含有淀粉酶,能将食物中的部分淀粉催化水解为麦芽糖,所以该选项不符合题意;

D、米饭中的糖类分解产物不是甘油,甘油是脂肪的分解产物,所以该选项不符合题意;

故选:B.

阅读理解

Do you know what your child is going to do when the school bell rings at the end of the day? More than 14 million students leave school every afternoon and have nowhere to go, since they do not have access to affordable after-school opportunities. According to the National Youth Violence Prevention Resource Center (NYVPRC), nine out of ten Americans think all youths should have access to after-school programs, but two-thirds of parents say they have trouble finding programs locally. The bad news is that situation may be getting worse.

After-school hours are the peak time for juvenile crimes and risky behaviors, including alcohol and drug use. The NYVPRC states that children who do not spend any time in after-school activities are 49 percent more likely to use drugs and 37 percent more likely to become a teen parent. Kids are also at the highest risk of becoming a victim of violence after school, particularly between the hours of 2p.m. and 6p.m.. The highest amount of juvenile crime occurs between 3p.m. and 4p.m. , when most children are dismissed from school.

The NYVPRC defines after-school programs as safe and structured activities that offer children opportunities to learn new skills. The skills students learn can range from technology and math to reading and art. Some programs also offer opportunities for internship(实习), community services , or mentoring. These programs have been shown to improve academic achievements, as well as relieve the stresses on working families. A report by the U.S. Department of Education and the U.S. Department of justice shows that students in after –school programs have fewer behavioral problems and more self-confidence , and can handle conflicts better than students who are not involved with these programs. In addition, according to the Harvard Family Research Project, after-school programs help students from low-income families overcome the inequities (不公平) they face in the school system.

小题1:What is the theme of the passage?

A.Prevention of juvenile crimes.

B.Risks kids face after school.

C.A research report on the stresses of students.

D.The benefits of after-school programs.小题2:Which of the following is TRUE according to the first paragraph?

A.Most parents don’t believe in after-school programs.

B.Students are not willing to attend after-school programs.

C.It’s difficult for parents to find after-school programs for their children.

D.Parents don’t care about where their children go after school.小题3:We learn from the second paragraph that __________________ .

A.the teachers should watch over kids after school

B.children are dismissed from school too late

C.after-school hours are a risky time for children

D.children should go home immediately school is over小题4:The author of the passage probably __________.

A.fully support after-school programs

B.doubts the effects of after-school programs

C.believes structured activities are useless for children

D.thinks students today are too stressed小题5:The underlined word “juvenile” in Paragraph 2 has a similar meaning to “_____” .

A.student

B.teenager

C.adult

D.campus

单项选择题