Final answer:
The correct word to complete the phrase is 'conozco'.
Step-by-step explanation:
The correct word to complete the phrase is conozco. The phrase 'conozco la abuela vieja' translates to 'I know the old grandmother' in English. The word 'conozco' is the first person singular form of the verb 'conocer', which means 'to know' or 'to be familiar with' someone or something.
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