Esherichia Coli and Clostridium Acetylbutylicum Are Reported to Be Derived

Esherichia coli and Clostridium acetylbutylicum are reported to be derived from a common ancestor. They both have similar but not identical gene sequences. Which of the following could best explain this difference in genetic coding?

A) They have a common ancestor, their DNA has been inherited from the common ancestor, therefore it will be similar.
B) The two species never diverged but they were discovered by two different scientists and therefore
Given different names.
C) These orthologs show identical gene segments, but the entire sequence has differences, therefore they are related through ancestoral genes.
D) Gene duplication created paralogs.
E) After the two species diverged, the genes accumulated random mutations that resulted in similar but not identical gene sequences.