to improve the flavors by increasing the sugar content to speed up the ripening of produce picked too early to partially cook the produce before canning or freezing to extend the shelf life by killing existing microorganisms
I gave my students this multiple choice question: Which of the following describes a reason why companies irradiate some fruits and vegetables before they are sold to the public?

Only one answer is correct among these 4 choices:
- to improve the flavors by increasing the sugar content
- to speed up the ripening of produce picked too early
- to partially cook the produce before canning or freezing
- to extend the shelf life by killing existing microorganisms

Could you tell me which one is correct?

to extend the shelf life by killing existing microorganisms