Which of these is a distinctive feature of scent hounds?

Scent hounds are a type of hound that primarily hunts by scent rather than sight. These breeds are hunting dogs and are generally regarded as having some of the most sensitive noses among dogs.

Hounds are hunting dogs that either hunt by following the scent of a game animal (scenthounds) or by following the animal by sight (sighthounds). There are many breeds in the scenthound type, and scenthounds may do other work as well, so exactly which breeds should be called scenthound can be controversial. Kennel clubs assign breeds of dogs to Groups, which are loosely based on breed types. Each kennel club determines which breeds it will place in a given group.

Scent hounds specialize in following a smell or scent. Most of these breeds have long, drooping ears. One theory says that this trait helps to collect scent from the air and keep it near the dog's face and nose. They also have large nasal cavities, which helps them smell better. Their typically loose, moist lips are said to assist in trapping scent particles.