請依下文回答第 11 題至第 15 題：
To counter the lost fertility that comes with harvesting crops and land-tilling, farmers have relied on regular
applications of human-made fertilizers to maintain field productivity. Excessive application of fertilizers can, 11 ,
further reduce natural soil fertility by introducing salts that kill microorganisms. Fertilizers can also provide an excess
of nitrogen that stimulates populations of 12 bacteria to the point that too little organic matter is available to feed
soil bacteria, which then starve. Nitrogen leaching into lakes can lead to unnatural algal blooms that can consume all of
the oxygen, 13 fish and plant life. When nitrogen contaminates domestic water wells, as has happened in
communities close to dairies and feedlots with inadequately controlled animal 14 , the “blue baby syndrome” can
result. Nitrates interfere with the oxygen-carrying ability of red blood cells and the effect can be especially serious for
infants. Most adults have an enzyme that converts the 15 red blood cells back to normal.
【題組】13 (A)stimulating (B) killing (C) kneading (D)shooting
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