The ground state (apart from normalization) of a particle of unit mass moving in a one-dimensional potential V(x) is exp(-x²/2)cosh(√2x). The potential V(x), in suitable units so that h = 1, is (up to an additive constant.) (a) x²/2 (b) x²/2 - √2x tanh(√2x) (c) x²/2 - √2x tan(√2x) (d) x²/2 - √2x coth(√2x)