In music notation, "piano" indicates a soft volume, while "forte" indicates a loud volume. Given the context of the question where the music suddenly becomes loud in the second section, Jessica would most likely see the term "forte" at the beginning of that section.
The other two options, "accelerando" (which means to gradually increase in speed) and "ritardando" (which means to gradually slow down), relate to tempo rather than volume. Therefore, the correct answer is:
forte