What does the log mean?

Examine the following traffic log; then answer the question below.

date-20xx-02-01 time=19:52:01 devname=master device_id="xxxxxxx"

log_id=0100020007 type=event subtype=system pri critical vd=root service=kemel

status=failure msg="NAT port is exhausted."

What does the log mean?
A . There is not enough available memory in the system to create a new entry inthe NAT port table.
B . The limit for the maximum number of simultaneous sessions sharing the same NAT port has been reached.
C . FortiGate does not have any available NAT port for a new connection.
D . The limit for the maximum number of entries in the NAT port table has been reached.

Answer: B