What was challenge in carroll v unites states

The main challenge of Caroll V. United States was warrant-less search of the automobiles.

EXPLANATION:

In the U.S of America, the Supreme Court allowed warrant-less searches of an automobile as it is not always possible to get a search warrant of an automobile that involves the movement of the vehicle from one location to another.

But the challenge court saw in this decision was search warrant was needed in the situations where automobile is not crossing the border. It was not very practical to check all the vehicle drives whether he consumed liquor or not.  People can move within the country lawfully. So, the warrant should be issued  whenever the driver breaks the law framed by the government.

quote is the answer your looking for.

it should be d or b but i'm sure it's d