def comment(language, block):
    """
    Return a block of a comment for a given language.

    If we don't know the language, we'll use # prefix.
    """
    if language in ('C', 'C++'):
        return "/*%s\n*/\n" % (block,)

    if language == 'BBC BASIC':
        prefix = 'REM '
    else:
        prefix = "# "
    lines = [prefix + line + "\n" for line in block.splitlines()]
    return "".join(lines)