Task: Question Answering
Input (English): Question: Counter Coulter® particle counter uses an electrolytic solution of: 
 Options:  <1> 0.9% lithium chloride in water. <2> Ammonium thiocyanate in hydrophilic solvent. <3> 15% lithium chloride in hydrophobic solvent. <4> 0.9% sodium chloride in water. <5> 0.9% sodium chloride in methanol.
Output (English): 4