单项选择题

Directions: You will hear three pieces of recorded material. While listening, answer each question by choosing A, B, C or D. You will hear each piece only once. Questions 11—13 are based on a report about obesity. You now have 15 seconds to read Questions 11—13. The researchers said "... which shows another potentially preventable public health disaster." What does "another potentially preventable public health disaster" here refer to