Ann, a user, needs to attend several day-long conferences and wants to ensure her mobile device will have enough power for these events. She is concerned about wall outlet availability at the conferences and needs to continuously use her device for important updates. Which of the following should a technician recommend to BEST accommodate Ann`s needs? 

Answer options:

A. Wireless charging pad
B. Built-in battery case
C. Extra charging cords
D. Airplane mode

B