Radon-210 is more radioactive than Technetium-99. Since Promethium-61 is more radioactive than Protactinium-234, it follows that Radon-210 is more radioactive than Protactinium-234. Any of the following, if introduced into the argument as an additional premise, makes the argument above logically correct EXCEPT: ['Promethium-61 and Radon-210 have equal levels of radioactivity.', 'Promethium-61 and Technetium-99 have equal levels of radioactivity.', 'Technetium-99 is more radioactive than Protactinium-234.', 'Promethium-61 is more radioactive than Radon-210.']