Answer: The correct option is d. the improvement of the microscope and microscopic techniques.
In the 1600s the development of cell theory was led by advances in microscopy. The cell theory is historic in terms of scientific theory. According to the theory it was proposed that all living organisms are made up from cells, cell is the basic structural unit in all the organisms and new cells arise from pre-existing cells. The continuous improvement of microscopy with time and advancements in magnification technology were enough for discovering the cells and contributed the most towards the cell theory.
I am pretty sure that the actual answer hides in the question itself, therefore I'd choose the second option. According to the phrase "he more successful of the two", it definitely should be B. Competition.
The origin of replication in E.coli is called the oriC
This region is rich in Adenine and Thymine bases because their base stacking interactions are weaker than those of Cytosine and Guanine.
Between A and T bases there are only 2 hydrogen bonds (not a very strong interaction so requires less energy to separate) while between C and G bases there are 3 hydrogen bonds (strong interaction thus requires more energy to separate)
The oriC is a region which needs to be separated when replication occurs. It is thus a region which requires easy separation with as little energy as possible so that proteins like DnaA can bind.
