单选题Directions:After reading the following passage, you will
find 5 unfinished statements or questions, number 36 through 40. For each
statement there are four choices marked A, B, C and D, you should make the best
choice and mark the corresponding letter on the Answer Sheet with a single line
through the center. Vitamin D is important to human
nutrition (营养) because it helps the body to absorb calcium (钙). Calcium is
essential for maintaining healthy bones and teeth. Vitamin D deficiency (缺乏症)
often leads to serious bone diseases. For this reason it is added to the milk
which is the staple food in most American people's diet. Our body requires
sunlight to make use of vitamin D. Only when ultraviolet rays from the sun
strike the vitamin D in our skin can the vitamin D be changed to its active form
and calciferol be produced by the sunlight. Calciferol is the substance that
carries the calcium to our bones. Therefore we can change vitamin D to its
active form without exposing our body to ultraviolet rays. Nor can we make use
of any of the calcium which we have consumed in our food. As a result, we will
suffer from a calcium deficiency and have weak bones. People with a calcium
deficiency, especially those who are over 40 years old, tend to break their arms
or legs when they fall or trip over something. If we want to ensure sufficient
vitamin D production in our body, we need to be exposed to sunlight for only 10
to 20 minutes every day. It is very easy for people to do unless in heavy smog
or cloudy days. Doctors recommend that people either drink milk or take vitamin
supplements or be exposed to the sun every day in order to avoid vitamin D
deficiency.
单选题
Which of the following is vitamin D's function?
A. It helps to maintain healthy bones and teeth.
B. It leads to serious bone diseases.
C. It helps the body to absorb calcium.
D. It helps to change calcium to its active form.
【正确答案】
C
【答案解析】[解析] 根据第一句话，可知答案为C。
单选题
Which is NOT the way of ensuring vitamin D sufficiency recommended by
doctors?
A. Staying in the sunshine about 10 minutes each day.
B. Taking vitamin supplements every day.
C. Drinking two glasses of milk every day.
D. Having at least eight-hour's sleep each day.
【正确答案】
D
【答案解析】[解析] “哪个不是医生建议的保证维生素充足的方法?”根据文章最后一句，可知答案为D。
单选题
What is the result of a person staying indoors all the time?
A. They can avoid sunburn.
B. They may have vitamin D deficiency.
C. They should break their legs every time they run.
D. They may put on much weight.
【正确答案】
B
【答案解析】[解析] “终日待在室内的人会有什么后果?”根据文章第8、9、10句，可知答案为B。
单选题
What do we need to change vitamin D to its active form?