【单选题】

Questions 11—13 are based on the following monologue about aspirin. You now have 15 seconds to read Questions 11—13. In what way can aspirin help heart surgery patients according to the doctorsA．Prevent losing blooD、

B．Help them keep awake.
C．Help people move blooD、
D．Prevent blood from thickening and blood vessels from being blockeD、