A sublattice(say, S) of a lattice(say, L) is a convex sublattice of L if _________
(a) x>=z, where x in S implies z in S, for every element x, y in L
(b) x=y and y<=z, where x, y in S implies z in S, for every element x, y, z in L
(c) x<=y<=z, where x, y in S implies z in S, for every element x, y, z in L
(d) x=y and y>=z, where x, y in S implies z in S, for every element x, y, z in L
I have been asked this question by my college professor while I was bunking the class.
This is a very interesting question from Graphs in portion Graphs of Discrete Mathematics