The correct answer is B) The marine inspector may require any boiler to be drilled to determine its actual thickness any time its safety is in doubt. This is correct because the Coast Guard regulations allow the marine inspector to require boilers to be drilled and thickness measured if there are any concerns about the boiler's safety or condition. This is a preventative measure to ensure the boiler is safe for continued operation. The other options are incorrect because: A) Drilling is not required at the first inspection after 10 years, B) is the correct statement, C) the boiler would not necessarily need to be condemned if thickness is less than original, and D) there is no requirement for a specific accuracy level for nondestructive testing devices.