The (i)____________ was potentially important for scientists studying the largest known three-dimensional manifold: the universe, seen as replete with mysteries that are imperceivable to most of the advanced astronomical instruments. Proving it mathematically, however, was far from (ii)____________. Most attempts were merely embarrassing, but some led to important mathematical discoveries. A. conjecture B. arduous C. corroboration D. facile E. formula F. illusory