B-24 Bomber At Willow Run
B- may refer to: *B-, a blood type *B- (grade), an academic grade *B − L In high-energy physics, ''B'' − ''L'' (pronounced "bee minus ell") is the difference between the baryon number (''B'') and the lepton number (''L''). Details This quantum number is the charge of a global/gauge U(1) symmetry in ...

Blood Type
A blood type (also known as a blood group) is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system. Some of these antigens are also present on the surface of other types of cells of various tissues. Several of these red blood cell surface antigens can stem from one allele (or an alternative version of a gene) and collectively form a blood group system. Blood types are inherited and represent contributions from both parents of an individual. , a total of 43 human blood group systems are recognized by the International Society of Blood Transfusion (ISBT). The two most important blood group systems are ABO and Rh; they determine someone's blood type (A, B, AB, and O, with + or − denoting RhD status) for suitability in blood transfusion. Blood group systems A com ...
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B- (grade)
This is a list of grading systems used by countries of the world, primarily within the fields of secondary education and university education, organized by continent with links to specifics in numerous entries. Africa Nigeria The choice of grading system at Nigerian schools depends on the institution and sometimes on the faculty of the institution. In addition, grading scales at university-level institutions have changed frequently. Grading scales can be 1 to 8, 1 to 4, or A through G, where A is on a 4.0 scale or on a 5.0 scale. The most common scale is now 1 to 7, with 9 being the highest grade obtained. In addition, degrees are awarded in a Class, depending on the grades received. Degrees may be awarded in the First Class, Second Class (Upper Division), Second Class (Lower Division), Third Class, and Pass Class. Grading scales for secondary certificates are standard. Below is the grading system of Nigerian universities: South Africa In South Africa, some universities fo ...
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