Which of the following statements are the reasons of American people’s obesity?

A、Americanlow-incomegroupsarenotawareoftheimportanceofhealthydiet.
B、Productsmadeofcheapcornarewidelyeatenbypeopleindailydiet.
C、Americanpeoplethinkobesityisnotharmfultohealth.
D、Workingpeoplearebusydoingtheirjobstosupportfamily,thereforetheyhavelittlechancenortimetodoregularphysicalexercise.