In which scenario is it possible to have the same directory number configured on two different lines
or phones and not be a shared line?

A.
directory number assigned to different partitions

B.
directory number assigned to the same partition

C.
directory number assigned to different calling search spaces

D.
directory number assigned to the same calling search space

Explanation:
You can set up one or more lines with a shared-line appearance. A Cisco Unified
Communications Manager system considers a directory number to be a shared line if it appears
on more than one device in the same partition.
Link:
http://cisco.biz/en/US/docs/voice_ip_comm/cucmbe/admin/8_6_1/ccmsys/a03dn.html#wp1100362