Which component of fertilizer is used for stimulating early growth purpose?

Which of the following is a potassic fertilizer?

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 ?

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 ?