Task: Question Answering
Input (English): Question: Iodine is poorly soluble in water ( 0.001M). Therefore, to obtain useful solutions as an analytical reagent it is dissolved in: 
 Options:  <1> 0.1 M potassium nitrate <2> Perchloric acid 0.01 M. <3> Excess of calcium nitrate. <4> Potassium iodide. <5> Hot water.
Output (English): 4