a) A continuous spectrum is given by incandescent (heated to several thousand degrees) solids, liquids and dense gases. A continuous spectrum is also given by high-temperature plasma, b) Each substance in a gaseous atomic state at low pressures (that is, under the condition of weak interaction of atoms with each other) has a line emission characteristic only for it.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.