Which of the following statements is true regarding visual testing?

The choice indicating that visual testing is limited to surface defects only is accurate. Visual testing (VT) primarily focuses on the examination of surfaces for imperfections that can be seen without the aid of equipment other than possibly magnifying tools or lighting enhancements. This method is effective in detecting surface conditions, such as cracks, corrosion, and other types of surface anomalies.

While VT can sometimes identify issues below the surface if surface defects indicate something deeper (like a crack that extends into the material), the fundamental limitation of visual testing lies in its inability to assess subsurface conditions effectively. It relies on visibility, which confines its capabilities primarily to the outer layer of materials.

The other options touch on aspects that do not fully characterize visual testing. For instance, it is not the most complex method; in fact, many consider it one of the simplest forms of NDT. Additionally, it does not require highly specialized equipment, as basic visual inspection can be performed with the naked eye. Finally, while visual testing is typically one of the first steps in an NDT process, it is not universally mandated to always be the first step, as the sequence can depend on the specific inspection protocol being followed.