The correct answer to this question is:
“The prediction is useful because it explains what observations will be made if a hypothesis is true.”
The prediction is important because it strengthens the outcome after a one year period. So for example if after one year there is indeed a decrease in the average height of the tomato plants, then we can definitely say that it is because of the presence of NoGro herbicide in the supplied water. The prediction also eliminates the need to find for other explanation why the height of the tomato plants shortened since it was already established in our prediction.