Tengo pensado I believe is the answer
The answer is <u>sonó</u>
Yo me duchaba cuando <u>sonó</u> el teléfono.
The verb duchaba is in pretérito imperfecto and matches with simple past (in this case sonó). This pretérito imperfecto describes an action or state in the past, without indicating whether it was completed or not.
1) la camiseta
This is because this is an item of clothing, whereas the other 3 words have to do with books.
