The difference between antibody allotypes and isotypes is that isotypes are ________ and allotypes are ________.

A) the differences in constant regions; differences within isotypes
B) differences within allotypes; the differences in constant regions
C) the differences in constant regions; alternations in the hypervariable regions
D) alternations in the hypervariable regions; differences within isotypes
E) alternations in the hypervariable regions of one person; alternations in the hypervariable regions among a species