What is a reason for these failures?

A user reports transfer failures from an IP phone for calls received from a PSTN to another PSTN number.

What is a reason for these failures?
A . The incoming calling search space of the SIP trunk does not include the partition of the line in the IP phone.
B . The service parameter related to Offnet to Offnet call Transfer is set to TRU
D . The IP phone is configured with the Wrong region.
E . The gateway is configured with the wrong device pool.

Answer: B