Answer: B
Analysis: The so-called online diagnosis means that the indicator control computer has self-diagnosis capabilities. Therefore, the answer is B.
Online diagnosis refers to the ability of a computer system to diagnose and detect equipment while it is running. In the field of industrial manufacturing, online diagnostics are important because it helps engineers and maintenance personnel quickly identify and resolve equipment failures, thereby improving production efficiency and quality.
Self-diagnosis capability means that the computer system can automatically detect and identify its own faults and problems, and give corresponding warnings or fault codes. Through self-diagnostics, computers can detect potentially faulty or damaged parts in time, thus avoiding downtime or loss of productivity.
Therefore, according to the "online diagnosis" and "indicator control computer" in the question stem, the self-diagnosis ability of answer B can be obtained.