Задайте 5 вопросов к предложению my mum and my sister are making a pizza.

1) who is your best friend? 2) what does she look like? 3) what do you like in your friend? 4) what are you both interested in? 5) do you quarrel sometimes? 6) what do you do together? 7) how much time do you spend together? 8) when did you meet last?  

she and her family live in london.

потому что это множественное число. они живут в лондоне.