Question

what might a zookeeper use to incapacitate an animal for transport?
a leash
a tranquilizer dart

Explanation:

A leash is used to control or guide an animal but not to incapacitate it. A tranquilizer dart contains a sedative that can make an animal calm or unconscious, which is suitable for incapacitating an animal for transport.

Answer:

a tranquilizer dart