Final answer:
Hansel and Gretel's story likely aids a detective by drawing parallels with the tale, suggesting a character in c) control of the robots, akin to the witch from the folktale. Its metaphorical essence often hints at the necessity of outsmarting a cunning adversary, potentially revealing such a character in the mystery plot.
Step-by-step explanation:
The story of Hansel and Gretel may offer various insights depending on the context in which it's referred to in relation to the mystery of robotic control. However, considering the typical storyline of Hansel and Gretel, one key aspect of the narrative is cleverness and resourcefulness in overcoming a witch who has control over their fate. If this folklore is used within a mystery plot, it's plausible that it serves as a metaphor or parallel to uncovering the controller of the robots. The story could provide an allegorical clue, rather than a technological or physical weakness, pointing to an individual whose cunning or deceptive nature must be outsmarted, much like the children had to outwit the witch.
Without additional context from the specific narrative in question, it’s challenging to identify the exact answer amongst the options provided. Nonetheless, the most likely scenario in which the story of Hansel and Gretel assists a detective is by introducing a character who is controlling the robots (option c). This is because the classic tale involves characters being cunning to deal with an antagonist who has control over their dire situation, which would be analogous to discovering a character behind the robotic manipulation.