Answer: A. estabas.
Explanation:
For this case we have the following statement:
While you ___________________ in the library, I was reading the newspaper in the park.
What we should do is fill in the blank with the correct verb.
The correct verb conjugated in the past simple is:
You were
We have then:
While you were in the library, I was reading the newspaper in the park.
The translation of the sentence in English is:
Mientras tú estabas en la bibloteca, yo estaba leyendo el periódico en el parque.
Hopes this helps!!
