When the rate of inflation exceeds the rate of return on the most profitable investment available, the difference between those two rates will be the percentage by which, at a minimum, the value of any investment will decline. If in such a circumstance the value of a particular investment declines by more than that percentage, it must be true that __ . Which one of the following logically completes the argument? ['the rate of inflation has risen', 'the investment in question is becoming less profitable', 'the rate of return on the most profitable investment available has declined', 'the investment in question is less profitable than the most profitable investment available']