Solar flares emit energy in three different stages. the precursor stage includes which of the following?

The precursor stage is the first of the three stages of solar flares. In this stage the sun triggers the release of magnetic fields and also in the precursor stage the first x-rays of the the magnetic flare can be detected. The precursor stage is followed by the impulsive stage and then the decay stage. I hope this helped. 

A.(nh4)(2co3)is the correct answer