New research is strengthening evidence that eating vegetables may be some of the best health advice. A study of 500, 000 Americans has found that just one extra serving of fruit or vegetables a day may reduce the risk of developing head and neck cancer. Many studies have shown that diet plays a role in cancer. Cancer experts now believe that up to two-thirds of all cancers come from lifestyle such as smoking, diet and lack of exercise. Tobacco and alcohol use increases the risk of head and neck cancer, which affects the mouth, nose, sinuses and throat.      Researchers at the National Cancer Institute asked men and women aged 50 and older about their diets, then followed them for five years to record all diagnoses of head and neck cancer, the sixth-leading cause of cancer-related death worldwide.      The study found eating six servings of fruit and vegetables per day per 1, 000 calories cut the risk of head and neck cancer by 29 percent compared to eating one and a half servings. An adult needs around 2, 000 calories a day. "One more serving of fruit or vegetables per 1, 000 calories per day reduced head and neck cancer risk by 6 percent,"said Neal Freedman, a cancer prevention fellow at the NCI.      A second study in 183, 000 people of California and Hawaii found a diet high in flavonols might help reduce pancreatic cancer risk, especially in smokers. Flavonols are common in plants but highest in onions, apples, berries, kale and broccoli.  The study found that people who ate the most flavonols reduced risk of developing pancreatic cancer by 23 percent than those who ate the least. All the following are the causes of the head and neck cancer EXCEPT   _  .
drinking smoking lacking exercise eating an apple