Anchor: A dog swims in the ocean with a surfboard.
Entailed: A dog is in the ocean.
Contradiction: A dog is running.
Contradiction: Britannia is not a place the queen can go to relax.  
Contradiction: 25% of fixed costs vary with volume.
Contradiction: The machine made ones have a distinct pattern on them.
Contradiction: A man in a t-shirt is skating.