问题：

[单选] What is a characteristic of Network Time Protocol？（）

A . NTP updates are sent in the timezone they are collected in，and the syslog server will adjust based  on the input time.
B . NTP authentication verifies the source，not the recipient.
C . NTP authentication requires that the recipient has multiple strata clocks to ensure accuracy.
D . Secure NTP can be configured to use SHA-1 hashing，since NTP is very insecure.
E . A stratum 0 clock should be configured at the core of every network，so it can connect to an accuratetime source.