💡 Detailed Explanation
The correct choice is 'なかなか' (not easily/not readily). When paired with a negative verb form ('〜ない'), 'なかなか' indicates that something is difficult to accomplish despite effort or expectation. Sentence translation: 'This homework is difficult, and it doesn't end easily.' 'ぜんぜん' (not at all) and 'あまり' (not very much) could be used with negatives but 'なかなか' perfectly denotes the progressive struggle of trying to finish the difficult homework. 'いつも' (always) is positive and does not fit.