Answer: C. open a cash account and invest in mutual funds holding high yielding common and preferred stocks
Explanation:
Investing in Mutual funds which hold high yielding common and preferred shares is the best option here. The dividends received will be high enough but will not be taxed too much as dividend tax is limited to 15% thereby saving the investment on taxes.
Also seeing as they will require the investment in other to buy a house in 5 years, they will need something that can be easily liquidated. Mutual funds are easy to liquidate from and so their investment here can be easily withdrawn when the time comes to allow them meet the house down payment.