Who fixed the technical fault of the mechanical teacher?

Correct answer: County Inspector

The County Inspector repaired the mechanical teacher when its geography sector had been adjusted too quickly for Margie. He was a trained technical expert who understood the machine's construction and settings. After examining it, he slowed the geography sector to a level suitable for Margie, showing that even an advanced educational machine could malfunction and require human maintenance. Option A is correct. Tommy's friend and a neighbouring child had neither the knowledge nor the responsibility to repair the device. An old human teacher was not called to fix it either; the inspector handled the technical problem. The incident also supports the story's broader idea that technology is useful but still depends on human expertise and judgement.