(A) A custom dimension
(B) Event tracking
(C) Scroll Depth is a standard Google Analytics metric.
(D) It’s not possible to track scroll depth with Google Analytics
You can track Scroll Depth in Google Analytics through Event tracking. You need to create a Custom Event and use Scroll variables for tracking how much the page was scrolled. You can use Custom dimensions in the event tracking to calculate the scroll depth using a percentage value. You can also use Google Tag Manager or other external plugins or chrome extensions to measure the page scroll depth.
This question is a part of the Assessment 3 section of the Google Analytics for Power Users course. You can find all the questions from all the four assessments with detailed explanation for this exam in our Google Analytics for Power Users Assessment Answers page.