(A) User-defined Constant variable
(B) User-defined Data Layer variable
(C) Built-in Event variable
(D) Built-in Click Classes variable
User-defined Constant variables are used when more than one tag uses the same Account number. So, if you want to use a variable for reusable Google Analytics Property ID then you need to select a User-defined Constant variable.
This question is a part of the Assessment 2 section of the Google Tag Manager Fundamentals exam. You can find all the answers to this exam in our Google Tag Manager Fundamentals Assessment Answers page.