Answer:
Here's an easy thing to remember!
AB blood types can receive any blood type.
O can donate to any blood type.
( - - ) ( + + ) Any positive blood can only go to positive blood. Same for negative.
A- => A-
O = O
AB => B
O- => B-
O- => A-
All of these are correct. (above)
And some incorrect examples. (below)
O- => O+
B => A
AB- AB+
A+ => A-
(hope this helps!)