I/ 1.A 2.B 3.C 4.D
II/ 1.C 2.D 3.C 4.D
III/ 1.your 2.him 3.My/yours 4.mine
5.theirs 6.Ours 7.her 8.Their
IV/ 1. The fuel is set on fire inside the rocket
2. The gases all go out the bottom of the rocket engine where it is open. They come out so fast and with so much power that the rocket is pushed up
3. The force of gravity tries to keep everything on the ground
4. Thrust is the force that pushes up against the front of the rocket
5. An airplane uses wings to help it fly
V/ 1. These pictures are ours
2. Julia will be thirteen next Friday
3. Is the black motorbike yours, Peter?
4. That invention isn't his
5. They predict that there will be a 10% car price increase
6. Solar panels will be installed on the roof of our house next week