💡 Detailed Explanation
'Ikanimo' is used to emphasize that something looks or seems exactly as it is described, meaning 'truly ~like' or 'looks just like ~'. It is often used with '〜rashii', '〜souda', or '〜youda'. Choice 1, 'ikanimo toshokan-rashii' (truly library-like), fits this pattern. The other choices would be more natural with different adverbs like 'shikiri ni' (repeatedly) for 2, 'zehi' (by all means) for 3, and 'hijou ni' (extremely) for 4.