Nancy's children have all grown and moved out. nancy is most likely to a. have a period of difficult transition. b. feel better if her children move back. c. have a more negative attitude about them returning home than her children do. d. feel liberated from child-rearing responsibilities.

The question refers to an "empty nest syndrome" - that is, the syndrome of people who used to live with their children, and who are used to never being alone, but whose children recently moved out, just like birds when then leave the nest. Those people can feel especially lonely in the beginning and might have hard time feeling ok when they are alone (but this usually goes away after some time). 

So the correct answer is:  to a. have a period of difficult transition