There wasn't nothing that could have been easier.
This is the correct choice because the sentence does not contain a double negative. The other choices either use two negative words within a single sentence or use an incorrect comparative form of easy.
940 MCQ for effective preparation of the test of Comparisons of English Grammar section.
Read the MCQ statement: There wasn't nothing that could have been easier., keenly and apply the method you have learn through the video lessons for Comparisons to give the answer. Record your answer and check its correct answer and video explanation for MCQ No. 89-4368.