G Aut(X) covers the convex hull of the rational points lying in the nef cone Amp(X).However, at the present time, this conjecture has been checked only for one non-trivial example by [7] and very little are known in general.On the other hand, in the course of his classification program of CalabiYau threefolds according to the behaviour of the second Chern class, Wilson ([26]) observed that the automorphism group of a Calabi-Yau threefold X, which is in general a discrete group, is actually finite if the second Chern class is positive, that is, C2(X) • D > 0 for all non-zero nef divisors D, and then asked : Question 1. Is the nef cone of a Calabi-Yau threefold with positive second Chern class a finite rational polyhedral cone?