ANS:B - nitrogen content is higher.

The statement "Urea is a better fertilizer than ammonium sulphate because nitrogen content is higher" is correct. While all the options listed have some relevance to the comparison between urea and ammonium sulfate, the primary reason for considering urea as a better fertilizer is typically its higher nitrogen content.

1. Nitrogen Content: Urea typically contains a higher percentage of nitrogen compared to ammonium sulfate. Urea generally has around 46% nitrogen by weight, while ammonium sulfate contains around 21% nitrogen. Since nitrogen is one of the essential nutrients for plant growth and is often the limiting factor in plant nutrition, fertilizers with higher nitrogen content are generally preferred for promoting plant growth and productivity.
2. Cost: Urea is often cheaper to produce than ammonium sulfate, primarily due to differences in manufacturing processes and raw material costs. However, the cost alone does not necessarily determine the superiority of a fertilizer.
3. Toxicity: Both urea and ammonium sulfate are generally considered safe for use as fertilizers when applied at recommended rates. However, excessive application of any fertilizer can lead to nutrient imbalances or environmental issues. Urea is not considered more or less poisonous compared to ammonium sulfate.
4. Manufacturing Ease: Urea and ammonium sulfate are both manufactured on an industrial scale using established chemical processes. While the ease of manufacturing may vary depending on factors such as raw material availability and technological advancements, this factor alone does not necessarily make one fertilizer better than the other.

In summary, the higher nitrogen content of urea compared to ammonium sulfate is the primary reason why urea is often considered a better fertilizer. However, the choice between urea and ammonium sulfate depends on various factors such as crop requirements, soil conditions, and economic considerations.