what are some rare blood types?
['AB-negative (. 6 percent)', 'B-negative (1.5 percent)', 'AB-positive (3.4 percent)', 'A-negative (6.3 percent)', 'O-negative (6.6 percent)', 'B-positive (8.5 percent)', 'A-positive (35.7 percent)', 'O-positive (37.4 percent)']