Refer to the exhibit. P1 and P3 cannot establish an LDP session between them. Which reason for this issue is true? 

Answer options:

A. Mismatched LDP discovery hold timers are between P1 and P3.
B. P1 is not configured to send LDP discovery packets to P3.
C. P3 cannot discover P1 because P3 has a route to each P1.
D. The LDP transport source address used on P3 is incorrectly configured.

D