Which of the following is$/$are true about functional and non$-$functional requirements for systems?

Group of answer choices

a$.$ Functional requirements are descriptions of the work the users need the system to do$.$

b$.$ Non$-$functional requirements are the qualities the system must have.

c$.$ Non$-$functional requirements are actions needed when the system is not functioning properly.

d$.$ a and b

e$.$ a and c