Final answer:
The appropriate noun to fill in the blank is 'sed' which means 'thirst' in English.
Step-by-step explanation:
Voy a comprar unas enchiladas porque tengo sed.
In this sentence, the appropriate noun to fill in the blank is sed which means 'thirst' in English. The verb 'tener' (to have) is used to express physical sensations such as hunger, thirst, cold, etc. In this context, 'tengo sed' means 'I am thirsty'.
Example:
'Voy a comprar agua porque tengo sed.'
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