2. The mistake is in A, the correct sentence is:
Bill and Sarah «were playing» in the garden when Sarah's mum «called» them in to have dinner.
3. The mistake is in B, the correct sentence is:
Claire «was» at her friend's house when the earthquake was «happening».
4. Mistake is in B, correct answer is “Grabbed”.
5. Mistake is in B, correct answer is “Heard”.