Step 1: Scale Relation:
\(\dfrac{C}{100}=\dfrac{F-32}{180}\). For a difference, the constant 32 cancels: \(\dfrac{\Delta C}{100}=\dfrac{\Delta F}{180}\).
Step 2: Substitute:
\(\Delta C=\dfrac{100}{180}\times54=\dfrac59\times54=30\).
Step 3: Check the Options:
35, 40 and 45 would need \(\Delta F=63,\ 72,\ 81\). The given difference is 54, so only 30 fits.
Final Answer:
The difference is \(30^{\circ}\)C, option (A).
\[ \boxed{\text{(A) } 30^{\circ}\text{C}} \]