Answer:
B. context clues
Step-by-step explanation:
All four options are useful and valid to determine the meaning of heatstroke in the text, however, the context clues strategy is the one that will give you a more accurate idea of the meaning of the word. This strategy consists of looking at the surrounding information of an unknown word in order to infer its meaning; and since the text is very descriptive about what this term is, by reading it, we can see all the context clues and learn that heatstroke is a "medical condition" and that "it occurs when the body’s internal temperature becomes so elevated that its cooling system begins shutting down".