Which of the Following Statements Explains Why the Thymine Analog

Which of the following statements explains why the thymine analog, 5-bromouracil (5-BU) , can cause mutations in DNA when it is inserted in place of a site normally occupied by T?

A) the bromine of 5-BU is similar in size to the methyl group of T and thus pairs with A
B) 5-BU is often found as the enol tautomer that hydrogens more effectively with G than with A
C) the bromine is subject to nucleophilic attack by a methyl transferase resulting in newly synthesized DNA being recognized as the methylated parent strand
D) the 5-BU is subject to removal resulting in a frame-shift mutation
E) none of the above