Cho dạng đúng của động từ trong ngoặc: The meeting room (equip) _____ with central heating system

Cho dạng đúng của động từ trong ngoặc 
1. The meeting room (equip) ________ with central heating system.
2. Look! The sheep and cows (graze) _______ peacefully on the lawn.
3. There didn't use (be) _______ electricity in our village 5 years ago.
4. We must (maintan) _______ our good traditions and customs.
5. John and I (be) ______ pen pals for nearly three years.