The u. s. supreme court upheld the practice of preventive detention in they argued that the practice protects the juvenile and society from pretrial crime.

The answer is in Schall v. Martin

Explanation:

In Schall v. Martin, the Supreme court supported a New York statute in which it was allowed the preventive detention of juveniles that were accused of a crime, and at the same time, these juveniles were considered a "serious risk" because they could commit other crimes before trial.

Schall v. Martin is considered the first time in which the Court sanctioned person's detention before establishing a person's guilt. This was made to ensure that the person would be at trial.  

answer; eliminate parking problems in cities, because a car took up only half as much space as a horse and buggy;