Final answer:
The appropriate word to fill the blank is 'mucho' which means 'a lot' or 'much' in English.
Step-by-step explanation:
The appropriate word to fill the blank in the sentence is mucho. So the correct sentence would be Estoy cansada mucho. The word mucho means 'a lot' or 'much' in English and is used to emphasize the level or intensity of something.
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