I don't get it. What's your question supposed to be???
The correct answer is - A. Desertification is increasing, and the desert is expanding.
The Sahara desert has been expanding in the past decades, and it has started to overtake territory south of it. This is mainly due to climate changes, the precipitation has been decreasing, the temperatures have been rising, so the desert has slowly crippled into the territories that were once steppes and savannas. There is an organized action from the people that leave on the borderline of the desert, where they have been thought some techniques as to how to stop the desert growing, and they have gladly accepted it and work hard on it. Initially it seems that there are positive results, but for sure only the time will tell.
The U.S. has more than 87,000 dams greater than six feet high (and two million overall). While many dams continue to provide benefits such as flood control, irrigation, and water supply, for other dams the cost of maintenance or the negative effects on communities, fish, and tribes justifies their removal.
Dam owners and regulators decide whether to remove a dam by weighing many factors including: the cost of removal and the ability to replace any lost power generation against avoided long-term maintenance; safety concerns; benefits to endangered fish populations; increased recreational and commercial fishing; and restoration of cultural values of nearby tribes.
By 2020, roughly 70% of dams will be more than 50 years old, inviting us to reconsider the value to the public of long-term investments in this infrastructure.
