24. The decimal numeral system is one of the ______ ways of expressing numbers. A) useful most world’s B) world’s most useful C) useful world’s most D) most world’s useful

16. Even at low levels, ______ A) the nervous system has produced detrimental effects by lead. B) lead’s detrimental effects are producing the nervous system. C) lead produces detrimental effects on the nervous system. D) the detrimental effects produced by lead on the nervous system.