Which statement correctly differentiates lossy and lossless compression?

• A. Lossy compression preserves all data; Lossless discards data
• B. Lossy compressions increase quality; Lossless decrease quality
• C. Both are reversible
• D. Lossy compression permanently discards some data; Lossless preserves all data

Answer: (D)

Understanding how data is treated during compression is the main idea. Lossy compression shrinks files by discarding some information during encoding, so the decompressed data is not exactly the same as the original. That data loss is permanent, which is why lossy formats are common for media where a tiny loss in detail is acceptable in exchange for a smaller size. Lossless compression reduces size but keeps every bit of information, so the exact original file can be restored after decompression. This distinction is why the statement differentiating them correctly is that lossy permanently discards some data while lossless preserves all data. The other descriptions misrepresent one or both types: they imply data can be fully preserved in lossy, or that both are reversible, or that quality improves with compression.