помогите под цифрой 3 ( а и b) пожалуйста дам 18 баллов

Спасибо большое

a. 3. It's a4. It's an5. They're6. It's an7. They're8. It's a.b. 1. coinS, penS, walletS, pencilS. 2. matches, sandwiches, watches, addresses. 3. diaries, dictionaries, countries, cities.