Mycoplasmas are type of prokaryotes which have no cell wall. Penicillin is an antibiotic which destroys the bacteria having cell walls.So penicillin cant destroy mycoplasma.The mycoplasmas can be destroyed by tetracyclins which are also antibiotics.Mycoplasma are sensitive to tetracyclins.Viruses are not sensitive to tetracyclin also. So the answer is tetracyclins.