Based on the given scenario, the best option for Ximena to do next would be option D - She should think about what else she is doing that might have made the bubbles bigger.
Since no one else was able to blow bigger bubbles by just facing the Sun, there might be some other factors that are contributing to the size of the bubbles that Ximena is blowing. By thinking about what other things she might be doing differently compared to her friends, Ximena might be able to discover what is causing the difference in bubble size.
This will help her understand her discovery better and may also help her friends achieve the same results. She can then demonstrate the technique to her friends and they can practice it together.