What happens when computers on a private network attempt to connect to the Internet
through a Cisco router running PAT?

A.
The router uses the same IP address but a different TCP source port number for each
connection.

B.
An IP address is assigned based on the priority of the computer requesting the connection.

C.
The router selects an address from a pool of one-to-one address mappings held in the lookup
table.

D.
The router assigns a unique IP address from a pool of legally registered addresses for the
duration of the connection.

Explanation:
http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/nat_staticpat.html
Static PATtranslations allow a specific UDP or TCP port on a global address to be translated to a
specific port on a local address. That is, both the address and the port numbers are translated.
Static PATis the same as static NAT,except that it enables you to specify the protocol (TCP or
UDP) and port for the real and mapped addresses. Static PATenables you to identify the same
mapped address across many different static statements, provided that the port is different for
each statement. You cannot use the same mapped address for multiple static NAT statements.
Port Address Translation makes the PC connect to the Internet but using different TCP source
port.