Final answer:
The correct answer to complete the sentence is "antes de" which means "before" in English.
Step-by-step explanation:
The correct answer to complete the sentence "Anotaré el número de teléfono" is B. antes de.
This phrase means "before" in English. So, the complete sentence would be "Anotaré el número de teléfono antes de leer el aviso." This translates to "I will write down the phone number before reading the notice."
Using the phrase "antes de" indicates that the action of writing down the phone number will happen before the action of reading the notice.
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