The correct option is B.
To avoid market risks, the best thing for Ali to do is to diversify his portfolio. Diversification of portfolio involves putting one's money in different types of investment. If one invests in 5 different type of investment, in case one experiences loss in one of them, he will still have four other investments, that will bring profits for him. But if an investor put all his money in one investment, he can lose everything if things doesn't go as planned.