Exam GRE Section 1 Verbal topic 3 question 15 discussion

Great achievers are by nature (i) _______, and therefore tend to be dissatisfied and discontent with their accomplishments no matter how great. Perhaps the
(ii) _______ modern example of this phenomenon was the eminent physicist Albert Einstein, whose theoretical breakthroughs in physics only raised new theoretical (iii) _______, which Einstein himself recognized and spent the last twenty years of his life struggling unsuccessfully to solve.