What is the exact theoretical percentage of nitrogen in pure urea and what form of nitrogen does it primarily provide to the soil upon application?

Options:

• A: 35% nitrogen, providing nitrate nitrogen directly to the plant roots.
• B: 46.6% nitrogen, providing amide nitrogen which is converted to ammonium and nitrate forms by soil enzymes.
• C: 21% nitrogen, providing ammonium nitrogen directly.
• D: 60% nitrogen, providing elemental nitrogen to the soil.

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