If two-parent with AB blood group claim and say that they have a baby with O blood group is born to them and it is their own baby and not adopted. Do you think they are speaking the truth?

Yes is possible to have a baby with different blood group.. Is not a guarantee that you will have the same blood group or a group closer to yours.

you need to include the text. we have no idea what you are referring to

answer; /// the above statement is (true);