Which should a critical annotation do?

My friends asked me, “are you not coming for the party? "change into passive voice

How can behavioral science be applied in improving public health? a.by tracking a disease to determine its sourceb.by creating promotions that improve health habitscboth by tracking a disease to determine its source and by creating promotions that improve health habitsd.neither by tracking a disease to determine its source or by creating promotions that improve health habits

The significant structural shift that happens between chapters 21 and 22 is