参考答案是C，我怎么觉得D对啊？
Q22:
In each of the past five years, Barraland’s prison population has increased.
Yet, according to official government statistics, for none of those years has there been either an increase in the number of criminal cases brought to trial, or an increase in the rate at which convictions have been obtained.
Clearly, therefore, the percentage of people convicted of crimes who are being given prison sentences is on the increase.
Which of the following, if true, most seriously weakens the argument?
A In Barraland the range of punishments that can be imposed instead of a prison sentence is wide.
B Over the last ten years, overcrowding in the prisons of Barraland has essentially been eliminated as a result of an ambitious program of prison construction.
C Ten years ago, Barraland reformed its criminal justice system, imposing longer minimum sentences for those crimes for which a prison sentence had long been mandatory.
D Barraland has been supervising convicts on parole more closely in recent years, with the result that parole violations have become significantly less frequent.
E The number of people in Barraland who feel that crime is on the increase is significantly greater now than it was five years ago.
