17. Trustee to be impartial.- Where there are more beneficiaries than one, the trustee is bound to be impartial, and must not execute the trust for the advantage of one at the expense of another. Where the trustee has a discretionary power, nothing in this section shall be deemed to authorize the Court to control the exercise reasonably and in good faith of such discretion. Illustration A, a trustee for B, C and D, is empowered to choose between several specified modes of investing the trust- property. A in good faith chooses one of these modes. The Court will not interfere, although the result of the choice may be to vary the relative rights of B, C and D.