Gram-positive cocci in clusters are characteristic of *Staphylococcus* species. The catalase test is a key biochemical test used to differentiate *Staphylococcus* species (which are catalase-positive) from *Streptococcus* species (which are catalase-negative). Therefore, statement C is true. Statement A is incorrect because *Streptococcus* species are typically arranged in chains or pairs and are catalase-negative. Statement B is incorrect because while it is a *Staphylococcus*, the catalase test alone does not definitively identify it as *Staphylococcus aureus*; a coagulase test would be needed for that. Statement D is incorrect; *Staphylococcus* species are generally resistant to bacitracin, which is used to differentiate Group A *Streptococcus* (*S. pyogenes*) from other streptococci.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.