Final answer:
The appropriate definite article for the noun 'tos' is 'los'.
Step-by-step explanation:
The appropriate definite article for the noun tos is los.
In Spanish, the definite article is used to specify a particular noun. The noun tos is a masculine plural noun, so the appropriate definite article is los, which corresponds to 'the' in English.
For example, if we want to say 'the cough' in Spanish, we would say 'los tos'.
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