Step 1: Understanding the Concept
\(\Delta G^{\circ}=-2.303\,RT\log K\).
Step 2: Substitute
\(-5700=-2.303\times8.314\times298\times\log K\)
\(2.303\times8.314\times298\approx5705\).
Step 3: Calculation
\(\log K=\dfrac{5700}{5705}\approx1\), so \(K\approx10\).
Final Answer:
The equilibrium constant is about 10.
\[ \boxed{\text{(B) }10} \]