crossing your legs until they feel numb can cause permanent nerve damage.

　　So next time you sit down, try to get yourself in the habit of sitting with both of your feet on the floor. Not only will it help your posture and stability, but it will also save your health in the long run.

28. What can we learn about crossing one's legs?

　A. It is a very bad social habit. B. It is usually practiced deliberately.

　C. It can do harm to people's health. D. It can make others feel uncomfortable.

29. According to the study, sitting with your legs crossed can______.

　A. affect your blood pressure B. resist gravity effectively

　C. lead to heart attacks easily D. improve the function of legs

30. In the third paragraph "pins and needles" probably means______.

　A. slight sharp pains B. being a little nervous

　C. serious muscle injuries D. being highly flexible

31. What is the main purpose of the text?

　A. To compare common habits. B. To give readers some advice.

　C. To evaluate effects of an experiment. D. To introduce research methods.

　　　　　　　　　　　　　　　　　D

　　Bees play a vital role in the world. Unfortunately, bees are dying by the second.

　　The main purpose of bees is to make honey. Honey, shockingly, does not exist for human consumption, it is essential to the insects. Honeybees store honey in their hives (蜂巢) in order for the bees to have energy for their flight muscles and for heating the hive during the winter period. They collect pollen (花粉) which supplies protein for young bees to grow.

　　According to Honey, com, the increased production and quality of agricultural crops as a result of honey bee pollination is valued &t more than1 $14/ 6 billion per year. These insects are responsible for over 70 of the fruits and vegetables we eat today, including apples, grapes, coffee, beans, and broccoli.

　　So if they are so valuable to agriculture, why do they keep dying off? A key suspect seems to be pesticides (农药). Honeybees who are exposed to pesticides result in the damage to their neurological (神经的) functions, specifically memory or behavior. And that's why the majority of worker bees disappear and leave behind a queen, plenty of food and a few nurse bees to care for the remaining immature bees and the queen. There are several other causes to the decline of bees, including the destruction of natural habitat, like woodlands, forests, and other habitats for bees. Climate change is also a factor in the decline of the wild bee population.

　　Actually, there are a variety of methods to help the bee population grow. One way is to start your own organic garden by planting bee-friendly plants. Pesticides are used in both industrial practices and even in your home, so it is best to find organic seeds and weed killers.

32. Why do honeybees store honey in their hives?

　A. To provide enough honey for human to consume.

　B. To draw protein out of honey for young bees.

　C. To help attract other insects and make hives stronger.

　D. To strengthen bee muscles and heat hives in winter.

33. Apples and beans are mentioned in the third paragraph to show that _.

　A. bees supply human beings with basic food

　B. bees mainly live on these agricultural crops

C. bees are of great importance to fruits and vegetables