The correct answer is commensalism.
Commensalism is a type of interaction between two species in which one species benefits from the interaction, while the other species is neither harmed nor benefited. In the case of Penicillium and Staphylococcus, Penicillium benefits from the interaction by being able to grow on the surface of Staphylococcus, while Staphylococcus is neither harmed nor benefited.
Predation is a type of interaction between two species in which one species, the predator, kills and eats the other species, the prey. In the case of Penicillium and Staphylococcus, Penicillium does not kill and eat Staphylococcus, so predation is not the correct answer.
Amensalism is a type of interaction between two species in which one species is harmed by the interaction, while the other species is neither harmed nor benefited. In the case of Penicillium and Staphylococcus, Penicillium is not harmed by the interaction, so amensalism is not the correct answer.
Mutualism is a type of interaction between two species in which both species benefit from the interaction. In the case of Penicillium and Staphylococcus, only Penicillium benefits from the interaction, so mutualism is not the correct answer.