Ψ is a function. What kind of output does this function have?

a. Ψ is always either only real or always only imaginary, and ∣Ψ∣² is the probability density
b. Ψ may be real or imaginary or a combination of both (a complex number), and ∣Ψ∣² is the probability density
c. Ψ is real where there is a non-zero probability of finding the particle at a location, and it is imaginary where the function has a zero probability of being
d. Ψ is the probability density, so it must have a real value.