根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。 选项中有两项为余选项。
Most of the earth’s freshwater sits underground. Tapping the groundwater has enabled farming in drier places. One example is the California Central Valley. 16 — Groundwater is what made this region’s crop production so bountiful.
17 Natural waterways will begin to empty, which can hurt freshwater ecosystems, including surface water — rivers and streams, which will begin to flow into the groundwater aquifer (含水层）.It will harm what is living in rivers and streams. Scientists consider this a tipping point. That’s when small actions can begin having an unusually big impact.
A new study has found that 15 to 21 percent of tapped watersheds have reached the tipping point. 18 Farmers in these areas mainly use groundwater to water their crops. At current pumping rates, it is predicted that 42 to 79 percent of watersheds will reach tipping points by 2050. “It’s really quite alarming，” says Inge de Graaf, a hydrologist (水文学者) who studies the distribution and circulation of the earth’s water. “Groundwater and surface water are closely linked. 19
A healthy groundwater aquifer protects ecosystems against seasonal ups and downs in the availability of water. 20 Moreover, it will maintain the biodiversity in the area. In the long term, it will benefit the human beings.
A. Pumping much groundwater can be harmful.
B. That provides stability for area plants and animals.
C. The earth’s water is all connected to one big circle.
D. That’s where about one-fourth of the US food comes.
E. Most of those tapped rivers and streams are in dry regions.
F. However, much pumping at this rate creates a ticking time bomb.
G. It means there will be a shortage of freshwater for human beings.
答案16-20 DAEFB
Most of the earth’s freshwater sits underground. Tapping the groundwater has enabled farming in drier places. One example is the California Central Valley. 16 — Groundwater is what made this region’s crop production so bountiful.
17 Natural waterways will begin to empty, which can hurt freshwater ecosystems, including surface water — rivers and streams, which will begin to flow into the groundwater aquifer (含水层）.It will harm what is living in rivers and streams. Scientists consider this a tipping point. That’s when small actions can begin having an unusually big impact.
A new study has found that 15 to 21 percent of tapped watersheds have reached the tipping point. 18 Farmers in these areas mainly use groundwater to water their crops. At current pumping rates, it is predicted that 42 to 79 percent of watersheds will reach tipping points by 2050. “It’s really quite alarming，” says Inge de Graaf, a hydrologist (水文学者) who studies the distribution and circulation of the earth’s water. “Groundwater and surface water are closely linked. 19
A healthy groundwater aquifer protects ecosystems against seasonal ups and downs in the availability of water. 20 Moreover, it will maintain the biodiversity in the area. In the long term, it will benefit the human beings.
A. Pumping much groundwater can be harmful.
B. That provides stability for area plants and animals.
C. The earth’s water is all connected to one big circle.
D. That’s where about one-fourth of the US food comes.
E. Most of those tapped rivers and streams are in dry regions.
F. However, much pumping at this rate creates a ticking time bomb.
G. It means there will be a shortage of freshwater for human beings.
答案16-20 DAEFB
苏19057182-3号