Without external forces, the third generation of a bacterium and the original parent cell will have approximately 87.5% matching DNA sequences, assuming binary fission (the typical method of bacterial reproduction). Each time the bacterium reproduces, it copies its DNA, and so, while the original parent's DNA is not entirely preserved due to potential mutations, the vast majority remains intact across generations.
However, as your provided answer options do not include this figure nor any approximation thereof, the closest relevant answer would typically be derived by examining the reproduction mechanics.
For understanding purposes:
- Generation 1: 100% matches the original.
- Generation 2: 100% of the DNA from Generation 1 (thus, 100% match).
- Generation 3: This generation comes from the second generation, thus maintaining roughly 100% match.
If we consider mutations found at each generation as a low percentage, it is possible for one to encounter theoretical approximations in various biological contexts, but without specific mutations spoken of or cycles calculated, the clearer answer stands at this high matching percentage.
For the sake of answering according to the offerings, 100% would be the most logical choice given the lack of any indication of mutations provided.