Task: Question Answering
Input (English): Passage: A variety of games for the FDS were released by Nintendo (including some like Super Mario Bros. which had already been released on cartridge) and third party companies such as Konami and Taito. A few unlicensed titles were made as well. However, its limitations became quickly apparent as larger ROM chips were introduced, allowing cartridges with greater than 128k of space. More advanced memory management chips (MMC) soon appeared and the FDS quickly became obsolete. Nintendo also charged developers considerable amounts of money to produce FDS games, and many refused to develop for it, instead continuing to make cartridge titles. Many FDS disks have no dust covers (except in some unlicensed and bootleg variants) and are easily prone to getting dirt on the media. In addition, the drive use a belt which breaks frequently and requires invasive replacement. After only two years, the FDS was discontinued, although vending booths remained in place until 1993 and Nintendo continued to service drives, and to rewrite and offer replacement disks until 2003. Question: Many FDS disks lack what?
Output (English): dust covers