Read the text, choose the correct options

A sniffer dog

    Do you know that dogs can work at customs and help policemen catch criminals? This profession, [which|that] is a very difficult one, is called a sniffer dog. These dogs can work at ports and airports. They detect baggage to help custom officers find some illegal objects. Criminals, [that|who] may be very dangerous, are often caught with the help of sniffer dogs. The dogs [which|who] work at customs always have a good sense of smell.    

1. Sniffer dogs work only at airports. [True|False]
2. Sniffer dogs detect baggage to catch criminals. [True|False]
3. Sniffer dogs sometimes have a good sense of smell. [True|False]