Ais a sudden eruption of magnetic energy released on or near the surface of the sun, usually associated with sunspots and accompanied by bursts of electromagnetic radiation and particles.
a) sunspots
b) prominence
c) solar flare
d) photosphere

They became more resistant.

A  reaction  in which  energy  is  released  to the surroundings is called an exothermic  reaction. in this type of  reaction  the enthalpy, or stored  chemical energy, is lower for the products than the reactants. when ammonium nitrate is dissolved in water,  energyis  absorbed  and the water cools.