It is always a good idea to extend the diversification of your equity portfolio geographically. And getting into China — the world's second-largest economy — can be particularly appealing. Here's a look at what are China-focused ETFs, whether they are worth investing in and how much you should hold in your protfolio.What are China ETFs?China ETFs are funds that track publicly listed Chinese companies. The issuing company purchases the underlying asset (such as stocks, bonds or currency), and investors purchase shares in the fund. As the underlying assets rise and fall, so does the value of your fund investment.However, investing…