Salazar made a chart to describe some relationships among species.

Relationships among Species
X Y
Boxing crabs gently carry anemones in their claws to sting predators and keep them away. The anemones feed off bits of food the crab drops. Fleas live on the warm body of a dog, biting the dog and eating its blood. The flea bites cause the dog to itch.

Which headings best complete the chart?

X: Competition
Y: Parasitism
X: Competition
Y: Commensalism
X:Commensalism
Y: Mutualism
X: Mutualism
Y: Parasitism