What is the UT near-surface 'dead zone' and how can it be minimized?

• A. A region where echoes are unreliable due to standoff and coupling; minimize with immersion, a different transducer, or shorter standoff.
• B. A region of maximum echo strength; minimize by increasing distance.
• C. A calibration offset; minimize by re-zeroing.
• D. An area with zero reflectivity.

Answer: (A)