Identify the error in each sentence and correct it.

Here are the corrections for the remaining sentences:

14. A pack of wolves attacked them!
15. Let us be calm and wait for the outcome.
16. The procurement officer has bought twenty reams of paper for the end of term tests.
17. There was barely any water in the tank.
18. The guest of the owner has just arrived.
19. We do not know the root cause of the problem.
20. My neighbour helped me to put out the fire.