A customer is reporting difficulty connecting some devices after replacing a wireless router with a new wireless 802.11ac router. The SSID, encryption and password are the same as the previous router. A technician goes on-site and notices the devices that are no longer connecting appear to be several years ago. Which of the following is MOST likely the problem? 

Answer options:

A. the password needs to be re-entered.
B. there is a security type mismatch.
C. there is insufficient antenna power.
D. there is a frequency mismatch.
E. the channel has changed.

D