Concept:Use the reversal of the chain rule for integration.Explanation:Let u=2x+1, so du=2dx, which gives dx=2du.Substitute into the integral: ∫(2x+1)3dx=∫u3⋅2du.Factor out the constant: 21∫u3du.Integrate using the power rule: 21⋅4u4=8u4.Replace u with 2x+1 and add the constant: 8(2x+1)4+C.Answer:8(2x+1)4+CThis matches option B.