Помогите. Ток чтобы 1000% было правильно

2 They are cutting down the trees now. 3 Building companies often cut down trees. 4 The school bell was ringing... 5 Listen! The school bell is ringing... 6 Does the school bell always ring...? 7 Sam and his friends are hiding... 8 Mr Brown usually hides... 9 The children  hid... 10 The workmen measured... 11 Look, they are measuring 12 ...always measure....