The correct answer is: Only argument I is strong.
Argument I is strong because it provides evidence that shifting agriculture is a wasteful practice. It states that shifting agriculture involves clearing a piece of land, farming it for a few years, and then abandoning it and moving on to a new piece of land. This practice can lead to soil erosion and deforestation.
Argument II is weak because it does not provide evidence that shifting agriculture is the only way to farm in areas where modern methods are too expensive. There may be other ways to farm in these areas that are less wasteful than shifting agriculture.
In conclusion, only argument I is strong.