Falsifiability is an important principle in science philosophy. A theory or hypothesis only be considered scientific if it has the possibility of rejection and acceptance. It means, before acceptance of hypothesis it must be disprovable.
Example: "All swans are white" is an example of falsifiability because black swans are also there.
we know this because A is her feeling sorry for her own misfortune. C and D are both a therapeutic statement because they are asking her to talk about it or take medicine.