A. How many children were there in Ava's family?

To answer this question, we need to refer to the text. The text mentions that 'When Ava was twelve years old, the family brought a cat'. This suggests Ava is one of the children. However, the text doesn't explicitly state the number of children in the family. Therefore, based on the information given, the most reasonable answer is that there is **one** child mentioned, Ava herself. Therefore, the answer is 1) one.