Ethel, in Her Home-Made Will, Leaves All Her Jewellery to Be

Ethel, in her home-made will, leaves all her jewellery to be held by Mark, her trustee, to distribute it to 'such of my needy old University friends who survive me, as Mark in his absolute discretion shall decide.' In relation to certainty of objects, which of the following statements is correct:

A) The trust is likely to be held uncertain, as there is no fixed list of all the potential beneficiaries provided.
B) Whether the trust will be held certain or not is dependent on whether there is evidential certainty as to how a potential object would prove they were within the class of objects.
C) Whether the trust will be held certain or not is dependent on whether the words create a conceptually certain class of persons from which Mark can select.
D) Whether the trust will be held certain or not is dependent on whether the criteria upon which Mark selects the potential beneficiaries is capricious or not.