Because you each had one positive and one negative gene. Positive is dominant over negative, so your resulting blood type is positive. When you produced offspring, your kid inherited the negative gene from each of you, and so the resulting blood type is negative.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.