Final answer:
The resistance across a diagonal of the square is 72 ohms. None of the above options are correct.
Step-by-step explanation:
To find the resistance across a diagonal of the square, we need to consider the arrangement of the wire. When a square wire is bent to form a closed square, the resistance across a diagonal is equal to the sum of the resistances across two adjacent sides of the square.
Since each side of the square has a resistance of 36 ohms, the resistance across a diagonal would be twice that, which is 72 ohms.
Therefore, the resistance across a diagonal of the square is 72 ohms.