The inability to realize that a problem can be solved by using a familiar object in an unusual way is likely due to

The answer is A) Functional fixedness. This is the tendency to see an object only in its usual function. A familiar tool stays locked in its everyday role, so we miss other uses that would solve the problem. Karl Duncker's candle problem (1945) is the classic demonstration: people struggled to fix a candle to a wall with tacks, matches and a box of tacks, because they did not see the empty box as a shelf.

• B) Rule bound approach is wrong. It describes rigid adherence to a procedure, not a failure to re-read what an object can do.
• C) Regulatory mechanism is wrong. It refers to control systems in organisms or institutions, which has nothing to do with cognition about objects.
• D) Limited capacity is wrong. It refers to the limits of working memory, such as Miller's 7 plus or minus 2 or Cowan's estimate of about 4 chunks. It does not explain why a known object is not reinterpreted.

This sits under mental ability and reasoning in the Prelims paper. For Mains, it links to creative problem solving and administrative innovation, where officers often fail to use existing resources differently.

Trap: Candidates pick B or D because they sound like cognitive or process terms. Ask what the question is actually describing: a failure to see a familiar object's other uses.