Which layer would hold the highest priority in this scenario?

Scenario: A Citrix Engineer created four application layers with different applications at different time stamps as shown below:

App Layer A C Microsoft Office Professional C 15/08/2019, 14:28

App Layer B C Adobe Acrobat Reader and Cisco Webex C 14/07/2019, 11:45

App Layer C C Active Directory Users & Computers, Citrix Studio C 20/08/2019, 16:10

App Layer D C Google Chrome and GoToMeeting C 27/07/2019, 10:35

Which layer would hold the highest priority in this scenario?
A . App Layer A
B . App Layer D
C . App Layer B
D . App Layer C