Final answer:
Maxwell's equations describe the behavior of electric and magnetic fields in various situations, explaining how electric fields are generated by charges and how magnetic fields are generated by moving charges or changing electric fields. They do not apply only to fields that are constant over time, are not limited to certain types of materials, and are not only valid in a vacuum.
Step-by-step explanation:
Maxwell's equations describe the behavior of electric and magnetic fields in various situations. They do not apply only to fields that are constant over time (option A), are not limited to certain types of materials (option B), and are not only valid in a vacuum (option C). Maxwell's equations are a set of four fundamental equations that explain the relationship between electric and magnetic fields and their sources, such as charges and currents. They describe how electric fields are generated by charges and how magnetic fields are generated by moving charges or changing electric fields (option D).