Which of the Following Statements Is FALSE Regarding the Triggers

Which of the following statements is FALSE regarding the triggers of the Tracking Area Update (TAU) messages?

A) A TAU is sent when an active UE moves into a new TA that is not in the UE's current Tracking Area Identity (TAI) list.
B) A TAU is sent when a UE moves from the 2G/3G network back to the LTE network.
C) A TAU is sent when an idle UE moves into a new TA that is not in the UE's current TAI list.
D) A TAU is required to be sent periodically.
E) A TAU is never required as long as an idle UE stays in the same TA.