Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: The rare earth metals are a set of seventeen chemical elements (the lanthanide series plus scandium and yttrium) that have particular importance for a variety of industrial processes and are used frequently in modern technology. Despite their name, rare earth metals are actually relatively abundant in the earth's crust. However, the extraction of many of these metals is quite difficult and has made their supply somewhat limited. They are highly sought after for this reason. Figure below shows the rare earth metals. Answer: rare earth metals
Output:
What do you call the set of seventeen chemical elements possessing particular importance for a variety of industrial processes, used frequently in modern technology?