ANS:C - Urea

Among the options provided, urea has the highest percentage of nitrogen.

• Urea [(NH2)2CO] typically contains around 46% nitrogen by weight, making it one of the most concentrated nitrogen fertilizers available.
• Calcium nitrate [Ca(NO3)2] contains calcium and nitrogen, but its nitrogen content is lower than that of urea. It typically contains around 15.5% nitrogen by weight.
• Calcium ammonium nitrate (CAN) contains both calcium and ammonium nitrate, but its nitrogen content is lower than that of urea. CAN typically contains around 26% nitrogen by weight.
• Ammonium sulfate [(NH4)2SO4] contains nitrogen in the ammonium (NH4+) form, but its nitrogen content is lower than that of urea. Ammonium sulfate typically contains around 21% nitrogen by weight.