In 2013, a report from The Nero England Journal of Medicine showed that increased body weight is related to the death rate for all cancers.  This is based on a study involving about 900,000 people, spanning many years.      The study, started in 1992 by the American Cancer Society, included men and women from all 50 states.  The youngest participants were 30  years old,  and the '8verage age was 57. By December 2008,  24%  of the participants  had died,  just a quarter of them from  cancers.  In analyzing  the  results, researchers  attempted   to  take account of  such  potential factors as smoking drinking alcohol,  taking aspirin and a wide variety of other factors that might otherwise affect the results.     The results are clear the more you weigh,  the greater your risk of dying of cancer will be (up to 52% higher for men and 62% for women). In men as well as women, the only cancers that did not have a strong connection with weight were lung cancer and-brain cancer.  For women, the strongest correlation with weight was uterine cancer ,which is 6.5 times higher for women  with a BMI(Body Mass Index)of 40 or more.  For men,  it was liver cancer,  which is 4.5 times higher in most obese men.     Smokers tend to be more successful in keeping weight off than non-smokers ,slightly reducing the risk ,But many of them don't have good lungs .Thus ,in another way ,they also face  risks.     As for why extra weight leads to excess cancer death rate ,there's no clear agreement .But the decrease in vitamin D in obese people seems a likely factor .Vitamin D is known to have a  role in preventing cancer .Also, there is a simple fact that obesity makes the management of  cancer more difficult .Although for now there is no simple answer to why obesity increases a person's cancer risk ,all we know for certain is that the risk is real. The author develops the passage mainly through  _  .
time order space order analysis and comparison figures and examples,
Question: In 2013, a report from The Nero England Journal of Medicine showed that increased body weight is related to the death rate for all cancers.  This is based on a study involving about 900,000 people, spanning many years.      The study, started in 1992 by the American Cancer Society, included men and women from all 50 states.  The youngest participants were 30  years old,  and the '8verage age was 57. By December 2008,  24%  of the participants  had died,  just a quarter of them from  cancers.  In analyzing  the  results, researchers  attempted   to  take account of  such  potential factors as smoking drinking alcohol,  taking aspirin and a wide variety of other factors that might otherwise affect the results.     The results are clear the more you weigh,  the greater your risk of dying of cancer will be (up to 52% higher for men and 62% for women). In men as well as women, the only cancers that did not have a strong connection with weight were lung cancer and-brain cancer.  For women, the strongest correlation with weight was uterine cancer ,which is 6.5 times higher for women  with a BMI(Body Mass Index)of 40 or more.  For men,  it was liver cancer,  which is 4.5 times higher in most obese men.     Smokers tend to be more successful in keeping weight off than non-smokers ,slightly reducing the risk ,But many of them don't have good lungs .Thus ,in another way ,they also face  risks.     As for why extra weight leads to excess cancer death rate ,there's no clear agreement .But the decrease in vitamin D in obese people seems a likely factor .Vitamin D is known to have a  role in preventing cancer .Also, there is a simple fact that obesity makes the management of  cancer more difficult .Although for now there is no simple answer to why obesity increases a person's cancer risk ,all we know for certain is that the risk is real. The author develops the passage mainly through  _  .
A. time order
B. space order
C. analysis and comparison
D. figures and examples,
Answer: