Option traders appear to be setting up for a bullish move on Market Vectors Agribusiness ETF (MOO). Traders plowed into 2,601 new call option contracts -- 20.81 times the average volume -- on the stock on Wednesday. And we know that traders were eager to get into this trade because 89% of the trades came in on the ask price.

The ETF closed Wednesday at $45.60, up 4.35% during the past month.

Based in London, Nick Vardy is among the leading international stock experts. The editor of The Global Bull Market Alert has created a package of stocks called the "Ultimate Defensive Global Bull Market Alert" Portfolio -- using ETFs to go short on China and the British pound while simultaneously going long on agriculture and the yen.

"UltraShort FTSE/Xinhua China 25 ProShares (ASE: FXP) has been a hero during market weakness. While the market's current focus is on the exposure of Chinese banks to U.S. subprime loans, the real issue in Chinese banks is their own bad loans to state-owned enterprises. China has a long way to fall.

"Short the CurrencyShares British Pound Sterling Trust (NYSE: FXB). With the U.K.'s fundamentals perhaps weaker than the United States, the U.K. currency should continue to weaken over the coming months.

"PowerShares DB Agriculture (NYSE: DBA) invests in some of the most liquid and widely traded agricultural commodities, corn, wheat, soy beans and sugar.

"Buy the Currency Shares Japanese Yen Trust (NYSE: FXY). The yen zigs when the rest of the market zags. A position in the Yen won't knock your socks off in terms of performance. But it will hold up well in times of turmoil and appreciate steadily as the 'carry trade' unwinds.

"A word of warning: This is a 'defensive' global portfolio that will hold up the best during periods of negative market sentiment. But understand that this is also the part of the portfolio that will underperform -- perhaps significantly -- on any 'relief rally' in the markets."

Each day, Steven Halpern's TheStockAdvisors.com offers the latest market commentary and favorite investment ideas from the nation's leading financial newsletter advisors.

Historically, currency trading had been done through futures accounts, making this the realm of sophisicated traders and currency professionals. But with the advent of exchange-traded funds that replicate movements in global currencies, even the novice can now participate.

I'd caution, that despite the ease with which one can now trade currency-based ETFs, understanding the inter-relationship of currencies and forecasting moves in individual currencies remain complex topics.

Two advisors with a long-standing expertise in this area are Mary Anne and Pamela Aden -- who offer their outlook for the US dollar, and their top picks among currency ETFs.

They explain, "Interest rates are an important influence in the currency markets." In their newsletter, The Aden Forecast, they continue, "Currently, U.S. interest rates are higher than the euro rate. But euro interest rates are rising and they're at a five year high, while the rise in U.S. rates is slowing down and the next direction for U.S. interest rates is likely down. That now makes the dollar unattractive and the euro more desirable.

In other words, the sisters explain, "The dollar's interest rate advantage has diminished and that's very bearish for the dollar."

This is serious situation, they note, especially since many countries are diversifying out of their dollar holdings. As an example, they cite China. The sisters observe, "China has formed a new agency that will diversify their massive trillion dollar reserves into other currencies."

In addition, they note, "As the dollar heads lower, other countries could speed up their diversification plans as well, which would help fuel the dollar's decline and boost the euro as demand for the euro grows."

If as they suggest, the US dollar is headed lower, then select foreign currencies will rally. To play this expected trend, the sister recommend that investors hold positions in foreign currencies through exchange-traded funds.

Their recommended positions are Australian Dollar Trust (NYSE: FXA), the Euro Currency Trust (NYSE: FXE), the British Pound Sterling Trust (NYSE: FXB), and the Swiss Franc Trust (NYSE: FXF).

For more stock picks from the leading financial newsletter advisors, visit Steven Halpern's free daily website, TheStockAdvisors.com.