Укажите в котором предложении допущена ошибка А-Does she get up late? Б-How much operes did Verdi write? В-Is Becky Miles

А-Does she get up late? (no mistakes)

Б-How much operas did Verdi write? (no mistakes)  

В-Is Becky Miles British? (no mistakes)

Г-Whats her nationality?  — What is her nationality? / What’s her nationality?

The mistake of this sentence is auxiliary verb. There must be an auxiliary after interrogative word. Instead of whats must be what is or what’s.