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....