I. Em hãy điền động từ “to be” thích hợp để hoàn thành những câu sau.
1. We are school children. We____________ thirteen years old.
2. – “How__________ you, John?” – “I ______________ fine, thanks.”
3. Those new desks___________ in their classroom.
4. My mother___________ cooking the meal in the kitchen now.
5. The students__________ camping yesterday so today they_________tired.