Final answer:
Solar flares are caused by the sudden readjustments of twisted magnetic field lines on the surface of the Sun, releasing electromagnetic radiation and sometimes coronal mass ejections (CMEs).
Step-by-step explanation:
Solar flares are caused by the sudden snapping and readjustments of twisted magnetic field lines on the surface of the Sun. These flares release a tremendous amount of electromagnetic radiation and sometimes eject large quantities of coronal material into interplanetary space, known as coronal mass ejections (CMEs). The extreme high temperature in sunspots is not directly responsible for causing solar flares.