The answer is b to support the authors opinion about oceans
1 The cars raced on the tracks. The hunter killed the animal by following its tracks
Sorry I don’t know two for felt
3 The survivors lit a fire to stay warm. The soldiers had to fire their guns.
4 I asked my friend to scratch my back. We had to back up to make room.
5+x
x represents the number, and "more than" indicates that it's addition.