阅读理解
You may know all about vitamin C, but do you know why vitamin D is also important to your body?
Experts from the Children's Hospital in Boston, US, have said that some teens don't get enough of
this important nutrient. Vitamin D is necessary for developing healthy bones. It is produced by the body
with the help of sunlight. It can also be found in certain foods and drinks, such as livers (肝脏) and eggs.
However, it is difficult to get enough vitamin D from food alone, which means enjoying the sunshine is
very important.
The doctors who ran the study tested 307 teenagers to discover how much vitamin D was in their
blood.
They found that 74 of the children tested nearly 25 per cent had vitamin D deficiency (缺乏).
Of those 74, 14 were severely short of the nutrient. The doctors also found that the amount of the
vitamin found in a child's blood was affected by a number of factors. Vitamin D levels drop in winter,
probably because less time is spent outside in the sunlight. Diet was also a key factor as well. Even skin
color has an influence, as people with darker skin find it more difficult to produce the vitamin.
Vitamin D deficiency can lead to many health problems for both children and adults. It is also believed
that low levels of it can cause depression (抑郁).
1. Vitamin D is important to your body in the way that it ______.
A. helps to keep your liver work normally
B. helps to build your bones
C. helps to produce fresh blood
D. helps to take in nutrient from food
2. We know from this passage that ______.
A. 25 percent of the teenagers in the world have vitamin D deficiency
B. vitamin D plays an important role in a child's blood
C. sunshine is one factor in gaining vitamin D for a human
D. the darker your skin is, the more vitamin D you'll get
3. The best title for the passage would be ______.
A. Vitamin D and Your Blood
B. Where to Find Vitamin D
C. Teenagers and Vitamin D
D. Don't Hide from the Sunshine
为
的中点，所以
的体积等于
的体积
中，
，而
，所以
即三棱锥
的高是三棱锥
，故选C