Passage Two
America put more people in prison in the 1990s than in any decade in its history. That started a debate over the wisdom of spending billions of dollars to keep nearly 2 million people locked up. According to statistics, the United States ends 1999 with 1983084 men and women in prisons. That shows an increase of nearly 840,000 prisoners during the 1990s and makes the United States the country with the highest prisoner population in the world. With the cost of housing a prisoner at about $20,000 a year the cost in 1999 for keeping all these prisoners behind bars is about $39 billion.
Some experts argue that the money is well spent, saying the cost of keeping prisoners behind bars doesn't seem much in comparison in the 1990s coincided with (与……相一致) a steady drop in the US crime rates. It is reported that serious crime has decreased for seven years in a row. "There are noticeable number of people who don't do crimes because they don't want to go to prison," they say.
36. There is a heated debate among American experts because ______.

America has put 2 million people in prison
B. the cost for housing a prisoner keeps rising
C. billions of dollars has been spent on prisoners
D. the prisoner population is the largest in the world