Q. 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