Whenever an artist endowed with both a high level of artistic skill and a high degree of creativity combines these two abilities in the process of creating an artwork, the resulting product is a great work of art. Moreover, no work of art can be great unless both of these elements are combined in its execution. Thus, great works of art are necessarily rare. Which one of the following is an assumption required by the argument? ['Not every artist possesses a high level of artistic skill.', 'An artist endowed with a high degree of creativity and a high level of artistic skill will necessarily produce great works of art.', 'A high degree of creativity and a high level of artistic skill are seldom combined in the creation of a work of art.', 'Anyone endowed with both a high level of artistic skill and a high degree of creativity will produce only a few great works of art.']