There are various reasons why cancers appear to be on the increase. For one thing, though their sufferers are to be found in all age groups, cancers are particularly likely to attack persons in their middle and advanced years. Naturally, since people live longer these years, there are more cancer sufferers than before. Again, with better methods of diagnosis  , doctors can more easily recognize cancerous growths that would formerly have passed unnoticed or that would have been wrongly diagnosed. It is also believed that certain habits and conditions of modern living, including heavy smoking and the pollution of the air, may leave people living in more cancer-causing conditions than before. We all look forward to the day when a simple medical test can find cancer while it is still small. Researchers around the world are working on _ . Most of their work deals with the examination of the blood. Researchers in Boston have found something in the blood of cancer patients that does not appear in healthy persons. The test showed which persons had cancer and which did not. It was correct more than 90 percent of the time. The researchers believe the test may be able to show cancer very clearly in its development. Cancers discovered early usually can be treated successfully. The test examines very small bits of fat in the blood called lipids  . Cancers seem to change lipids although doctors do not know why. The test showed differences between the lipids of the persons with cancer and the lipids of those without cancer. The researchers say the new test could be a step to develop a simple way to check patients for cancer before the disease shows on an X-ray. Which of the following statements is true according to the passage?
Cancers have much to do with something in patients' blood. People living in better conditions are most likely to be attacked by cancer. X-raying is the best way to determine whether a person has cancer or not. Cancers have nothing to do with a person's habits and living conditions.