ANSWER: C, the continents were at one time joined together.
REASONING: Alfred Wegener was the first person to propose the scientific theory of Continental Drift. Continental Drift is a theory that supposes all the continents were at one time joined together as one large land mass. The mechanisms of continental drift can be explained by Plate Tectonics.
If the cell has a cell wall you know it is a plant cell.
If you talk about the process of fission in the nuclear field then the most used is U-235 because is the easiest to use. Have in mind that the majority of uses of uranium is U-238 but the easiest to be used is U-235
