Exam 300-810 topic 1 question 110 discussion

A is correct

I guess should be A. https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/im_presence/configAdminGuide/12_5_1/cup0_b_config-and-admin-guide-1251/cup0_b_config-and-admin-guide-1251_chapter_010010.html Example : If you plan to enable Multiple Device Messaging, measure deployments by the number of clients instead of the number of users as each user may have multiple Jabber clients. For example, if you have 25,000 users, and each user has two Jabber clients, your deployment requires the capacity of 50,000 users. On this scenario, 30,000 users has 3 devices : 30,000*3 = 90,000.