Refer to the exhibit, which as-path access-list regular expression should be applied on R2 as a neighbor filter list to only allow update with and origin of AS 65503?
A. _65509.?$
B. _65503$
C. ^65503.*
D. ^65503$
E. _65503_
F. 65503
Which as-path access-list regular expression should be applied on R2 as a neighbor filter list to only allow update with and origin of AS 65503?