Which Is the Correct Statement About User Activity (In the Context

Which is the correct statement about user activity (in the context of HCI) :

A) User activity refers to the operation of a computer system;
B) Staring at a computer screen without reading or thinking is also a kind of user activity;
C) Physical resources are the only kind of resources involved in user activity;
D) User activity can be analyzed at multiple levels using TSSL model;
E) The analysis of user activity has nothing to do with the context.