Proofs by counter example

Question

Suppose R and S are relations on the set X.

1. R is symmetric → R' is antisymmetric
2. R and S are transitive → R ∪ S is transitive
3. R and S are antisymmetric → R ∪ S is antisymmetric

I'm having trouble thinking of and proving a counter example for these 3. Any ideas or help would be very appreciated.