Which of the following infix expressions is obtained on converting the postfix expression A B - C + D E F - + $?

Correct option is B

Step-by-Step Conversion of Postfix to Infix:

We’ll use a stack to convert postfix to infix.

Given Postfix Expression:
A B - C + D E F - + $

Let’s process it left to right:

1. Push A, B → Stack: A, B
2. - → Pop B, A → Push (A - B)
   → Stack: (A - B)
3. Push C
   → Stack: (A - B), C
4. + → Pop C, (A - B) → Push ((A - B) + C)
   → Stack: ((A - B) + C)
5. Push D, E, F
   → Stack: ((A - B) + C), D, E, F
6. - → Pop F, E → Push (E - F)
   → Stack: ((A - B) + C), D, (E - F)
7. + → Pop (E - F), D → Push (D + (E - F))
   → Stack: ((A - B) + C), (D + (E - F))
8. $ → Pop (D + (E - F)), ((A - B) + C) → Push (((A - B) + C) $ (D + (E - F)))

Now expand and format:

Final Infix Expression: A - B + C $ D + E – F

This matches option (b).

Important Key Points:

1. Postfix to infix conversion uses a stack and binary operator evaluation.
2. The operator $ (typically custom-defined) is treated like any binary operator here.
3. Proper parenthesis are used during evaluation but omitted in final flattened form when no precedence/associativity is explicitly defined.

Knowledge Booster:

• Option A: Misplaces $ between C and D too early, disrupting actual evaluation order.
• Option C: Misplaces $ between B and C, which never occurs in postfix parsing.
• Option D: Starts with A + B, which never happens as the first operator in actual stack processing.