Let L be a set with a relation R that is reflexive, antisymmetric and…

Let L be a set with a relation R that is reflexive, antisymmetric and transitive. Also, for every pair of elements a, b ∈ L, the least upper bound lub(a, b) and greatest lower bound glb(a, b) exist. Which of the following are true?

a) L is a poset.
b) L is a Boolean algebra.
c) L is a lattice.
d) None of the above.