What Are the Three Main Principles of Usability Testing

What are the three main principles of usability testing?

A) Usability testing permeates product development.
B) Usability testing involves studying real users as they use a product.
C) Usability testing replaces quality assurance testing.
D) Usability testing involves setting measurable goals and determining whether a product meets them.
E) Usability testing is essential for every document.