Here, we need to understand the keywords. In specific, Boldface portions herein means the most notable arguments, the most contrasting lines in the argument. so, let's ride on.

In Option A - CORRECT.
The author seeks to differentiate to the audience reading that swimming water that has salt has various disadvantages which he enumerated into two. He also went on to talk about the perceived disadvantages which can be seen in the later part of the statement. Very appropriate way to summarize the author's note.

In Option B - INCORRECT.
Know that it's true that the first part is unproven because the statement backing it up is from the owner so he could be partial nevertheless, the points made by the manufacturers of pool chemicals is not enough to negate the bold claim by the operators of such swimming pools.

Option C - INCORRECT.
The first portion of the statement could never be the concluding part because they are two opposing sides, one from the owner and the other from the chemical producers. It's also wrong in the second part because an unintended statement cannot be deemed to negate a whole statement credited to the opposing side in a debate.

Option D - INCORRECT.
This is true though because it enumerates the pros and cons but where this option got it wrong was where it said ''directly refutes''. The whole relation is an unrelated one. Two closely related argument but not the same.

Option E - INCORRECT.
Being the last option. The first part could be a claim truly because it's coming from someone who should market his product not de- market it, while the second part is not directly related but closely a competing statement.