A
(2019·辽宁五校协作体联考)In the dead of winter，we don’t typically think about spending time outdoors，but according to many physicians we should．The sun is our greatest source of a vitamin that is essential for good health—Vitamin D.
This important vitamin strengthens bones and teeth and is linked to the prevention of heart disease，cancer and many other lifethreatening diseases．The recommended daily requirement is 400－600 International Units (IU). In summer, people with dark brown eyes and darker skin turn sunlight from just 15 minutes outside without sunscreen into adequate amounts of Vitamin D.
Even during winter, just a 10minute walk at midday can keep the body’s Vitamin D at healthy levels．During brief winter walks，we receive the greatest benefits when we wear no sunscreen and expose as much skin to the sun as possible.
Vitamin D can be also obtained from foods．Salmon is one of the best sources of the Vitamin. Egg yolks(蛋黄)，cheese，mushrooms and some animal organs contain smaller quantities of it.
To attract consumers，food companies add Vitamin D to some of their milk products．The practice of putting the Vitamin into milk began in the 1930s．At that time，many children were suffering from rickets，an illness that is caused by a deficiency(缺乏)of Vitamin D．It made the children’s bones soft and weak．Adding Vitamin D to milk helped to solve the problem, and it has been available ever since.
For people who still need more Vitamin D, there is another option. Take Vitamin D supplements(补充物)．These products are widely sold in stores．However，anyone considering taking supplements should consult a physician first.
【解题导语】 本文是一篇科普文。文章主要介绍了维生素D的一些情况。
1．During the winter months，people________.
A．aren’t able to meet their deadlines
B．often don’t dress warmly enough
C．generally like to remain indoors
D．leave lots of work for others to do
C 解析：细节理解题。根据第一段中的第一句可知，在冬天人们愿意待在室内。
2．According to the text，Vitamin D________.
A．can be obtained by being exposed to the sun
B．can be used to cure lifethreatening diseases
C．can be mainly found in some milk products
D．can make the children’s bones soft and weak
A 解析：推理判断题。根据第一段第二句以及第三段第一句可知，维生素D可以通过晒太阳获得，故选A。
3．Why is salmon mentioned in this article?
A．It’s seldom prepared in the correct way.
B．It’s a useful addition to a person’s diet.
C．It has a huge impact on the environment.
D．Its advantages have been exaggerated.
B 解析：推理判断题。根据第四段可知，三文鱼是补充维生素D的食物，因此对我们的饮食是有用的补充物，故选B。
4．The main purpose of this article is ________.
A．to introduce a valuable nutrient
B．to advertise Vitamin D supplements
C．to note risks associated with a nutrient
D．to explain how a nutrient was discovered
A 解析：写作意图题。根据全文可知，本文主要介绍一种营养成分——维生素D。
