A、Countless tree limbs. B、A few skeletons. C、Lots of wrecked boats and ships. D、Millions of coins on the bottom. D事实细节题。新闻中提到，19

New York State plans to shut off the thundering waters of Niagara Falls—again. At least, the American side of the falls. This "once in a lifetime" event actually may take place twice in some folks’ lives. The New York State parks system wants to turn off the falls on the American side sometime in the next two to three years to replace two 115-year-old stone bridges that allow pedestrians, park vehicles and utilities access to Goat Island.
    The American side of the falls were shut off in 1969 to study the buildup of rock at the base of the falls. When that happened, people came from all over the world to see the falls turned off.
    People are curious by nature. They want to see what’s underneath. In fact, those who first came to have a look did see something. They found millions of coins on the bottom.
    1. Why does New York State want to turn off Niagara Falls?
    2. What did people find when Niagara Falls were shut off in 1969?