Questions26-30are based on the following chart:

Cigarette Smoking by Grade Level: 2005-2009

26. The purpose of the chart is to show________

A. the percentages of smokers in schools

B. the increase of smokers in grades 9-12 during 2005-2009

C. the number of teenage smokers in grades 9-12

D. the amount of money spent by young smokers- over the years

27. Which grade had the highest percentage of smokers in 2005????

A. The 9th. B. The 10th.

C. The 11th. D. The 12th

28.The percentage of the 9th grade smokers in 2009 was ______

A. 23.2 B. 25.2

C. 31.2 D. 33.4

29. Which grade saw the greatest increase of smokers over the four years?

A. The 9th. B. The 10th.

C.The11th可 D. The 12th.

30. What tendency can we find from the chart?

A .Smokers in all grades have increased.

B. The higher the grade， the more the smokers.

C. The older a student， the more he smokes.

D. Low graders smoke less heavily.