Alternativa correta: a) Alfanuméricos (letras e números), hexadecimais, espaço e tabulação
POSIX Description ASCII Unicode Shorthand Java
[:alnum:]Alphanumeric characters[a-zA-Z0-9][\p{L}\p{Nl}
\p{Nd}]\p{Alnum}
[:alpha:]Alphabetic characters[a-zA-Z]\p{L}\p{Nl}\p{Alpha}
[:ascii:]ASCII characters[\x00-\x7F]\p{InBasicLatin}\p{ASCII}
[:blank:]Space and tab[ \t][\p{Zs}\t]\h\p{Blank}
[:cntrl:]Control characters[\x00-\x1F\x7F]\p{Cc}\p{Cntrl}
[:digit:]Digits[0-9]\p{Nd}\d\p{Digit}
[:graph:]Visible characters (anything except spaces and control characters)[\x21-\x7E][^\p{Z}\p{C}]\p{Graph}
[:lower:]Lowercase letters[a-z]\p{Ll}\l\p{Lower}
[:print:]Visible characters and spaces (anything except control characters)[\x20-\x7E]\P{C}\p{Print}
[:punct:]Punctuation and symbols.[!"\#$%&'()*+,
\-./:;?@\[
\\\]^_`{|}~]\p{P}\p{Punct}
[:space:]All whitespace characters, including line breaks[ \t\r\n\v\f][\p{Z}\t\r\n\v\f]\s\p{Space}
[:upper:]Uppercase letters[A-Z]\p{Lu}\u\p{Upper}
[:word:]Word characters (letters, numbers and underscores)[A-Za-z0-9_][\p{L}\p{Nl}
\p{Nd}\p{Pc}]\w
[:xdigit:]Hexadecimal digits[A-Fa-f0-9][A-Fa-f0-9]\p{XDigit}
Fonte: http://www.regular-expressions.info/posixbrackets.html