According the keown book, which web-based personal financial planning website is known as "the best free way to manage your money? " a. mint. comb. levelmoney. comc. yahoofinance. comd. wsj. com

Mint.com

Explanation:

Mint.com: It is a free, and web-based personal management service that manages finance in the US and Canada, and has been developed by Aaron Patzer. It at the beginning used to leverage users to link various of their financial accounts via the deal with the Yodlee, however, since then it has started to take the services of the intuit to connect all the financial accounts of a user altogether.

The Level Money provides the details that help in understanding the cash flow through the automatic income detection and expenses that are fixed.

WSJ.com

This site provides the latest news.

YahooFinance.com

And this one provides the stock quotations for free, latest news, social interaction and mortgage rates, and resources for portfolio management.

Hence, the correct option is Mint.com. And we can find this in  Keown book as well.