If the modulus is 4 and the real part is –2.0, what is the imaginary part?

For a complex number, the modulus satisfies 4² = 2.0² + (imaginary part)². Thus the imaginary part has magnitude √(16 − 4) = √12 ≈ 3.46, which rounds to 3.5. So the matching choice is 3.5.

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