Refer to the exhibit. 

A network engineer is troubleshooting a NTP synchronized issue in CUCM. Why is NTP unsynchronized? 

Answer options:

A. The NTP server used is a Windows based NTP server.
B. The IOS Command NTP server 172.25.140.151 version 3 is advertising NTPv3.
C. The NTP server stratum is higher than four.
D. A firewall is blocking NTP port 123.

B