C. I = 4.2A.
The magnetic field inside a solenoid is given by the equation:
B = μ₀NI/L
Clearing I for the equation above.
I = BL/μ₀N
With B = 1.0T, L = 3 x 10⁻²m, μ₀ = 4π x 10⁻⁷T.m/A and N = 5748turns
I = [(1.0T)(3 x 10⁻²m)]/[(4π x 10⁻⁷T.m/A)(5748turns)]
I = 4.15 ≅ 4.2A