The argument proposes that the legislature's plan to implement tax-free savings accounts for investors will improve the long-term savings rate of the citizens of Levaska. To support this prediction, we need an answer choice that shows the plan will encourage long-term savings.

Option B, stating that the majority of people choosing to take advantage of the tax-free savings accounts will withdraw their money prior to age sixty-five, weakens the argument, so it cannot be the correct answer.

Option A has no information on whether the tax-free savings accounts will encourage long-term savings, so it is not the correct answer.

Option C supports the idea that the tax-free savings accounts will encourage long-term savings, as it indicates that many citizens of Levaska will invest in these accounts well before the age of sixty-five. This implies that they plan to save for the long-term, and therefore, option C is the correct answer.

Option D weakens the argument by indicating a decreasing trend in long-term savings in Levaska, and option E is irrelevant to the argument.

Hence, the correct answer is (C).