The correct answer is (a).
The coefficient of variation is a measure of the volatility of an investment relative to its expected return. It is calculated by dividing the standard deviation of the investment by its expected return. A higher coefficient of variation indicates a more volatile investment.
In this case, the coefficient of variation for investment A is 30%, while the coefficient of variation for investment B is 7.5%. This means that investment A is more volatile than investment B.
Option (b) is incorrect because investment B has a lower coefficient of variation than investment A. Option (c) is incorrect because we can conclude that investment A is more volatile than investment B. Option (d) is incorrect because (a) is the correct answer.