what has x in it?
['2 letters. AX EX OX XI XU.', '3 letters. AXE BOX COX DEX DUX EXO FAX FIX FOX GOX HEX HOX KEX LAX LEX LOX LUX MAX MIX MUX NIX NOX OXO OXY PAX PIX POX PYX RAX REX SAX SEX SIX SOX TAX TEX TIX TUX VEX VOX WAX WEX WOX XIS YEX ZAX ZEX XED.', '4 letters. ... ', '5 letters. ... ', '6 letters. ... ', '7 letters.']