We prove the following statement using element proof and contradiction. For all sets B and C, (B-C) - B = { } Which statement is the initial supposition in the proof? Let B and C be some sets where (B-C) -B is not empty and let x be any element in (B-C) - B Let B and C be any sets where (B-C)-B ={} and let x be any element in (B-C)-B Let B and C be any sets where (B-C)- B = {} and let x be any element in C Let B and C be some sets where (B-C)-B is not empty and let x be an element in (B-C) - B