Which one of the following statements about fertilizers is not correct?

Which one of the following is not a nitrogen fertilizer?

Which one among the following fertilizers is a source of nitrogen ?

Which of the following is a potassic fertilizer?

Fertilizers are used to obtain higher yields of crops. However, all nutrients are usually not available in fertilizers. Which one of the following nutrients is usually not available in fertilizers ?

Which of the following is a Kharif crop?