The worker in the argument reasons that there will be no need for her to trim the overhanging branches of a certain tree because the owners of the tree have indicated that they might cut it down anyway.
But, the owners have indicated that they MIGHT cut it down. This means that they may not cut it down, and in this case if the worker does not trim the branches, then she will not have prevented against anticipated damage to the power lines because of the impending stormy season.
Similarly, answer choice (C) follows the same reasoning. Answer choice (C) reasons that the mechanic will not have to replace one of the vans brakes since it is tentatively scheduled to be junked.
However, the key is that it is only TENTATIVELY schedule to be junked. Just as in the passage, this still leads open the possibility that it won't happen, i.e. it won't be junked, which means that the mechanic did no ward away any danger or damage since he did not replace the worn brakes on the van.
Hope that clears things up! Please let us know if you have any other questions.
