Which has a higher range of concentration, alkalinity concentration or sulfate concentration?
return alkalinity concentrations ;return sulfate concentrations ;return the  highest of #1 ;return the  lowest of #1 ;return the  highest of #2 ;return the  lowest of #2 ;return the  difference of #3 and  #4 ;return the  difference of #5 and  #6 ;return which is higher of #7 ,  #8
['select', 'select', 'aggregate', 'aggregate', 'aggregate', 'aggregate', 'arithmetic', 'arithmetic', 'comparison']