Search and Rescue Dogs Read the following excerpt:

Search and rescue dogs (SARs) are not just born. They require a huge investment of time, dedication, training, and patience almost from the day they are born. SAR dogs are carefully selected when they are quite young. Trainers look for dogs that lack aggression and respond well to commands. They also look for a certain mental focus—it can be on a type of play or a special toy—that will enable the dog to work at a single task for a long time. This focus is important to the training of the dog, but also will be required when the dog is searching for and following human scent.

Which of the following explains the central idea in the text above?

SAR dogs are born talented trackers.
SAR dogs are not always quick learners.
SAR dogs must bond with their trainers.
SAR dogs must have special qualities.