crux

n. 十字架形,关键,难题

crumble, crumbling, crumbly, crumbs, crummy, crumpet, crumple, crunch, crunchy, crupper, crusade, crusader, crush, crush barrier, crushing, crushingly, crust, crustacean, crusty, crutch, cry, cry down, cry for, cry off, cry out, cry-baby, crybaby, crying, cryogenic, cryogenics, crypt, crypt(o)-, cryptic, cryptically, cryptogam, cryptogram, crystal, crystal ball, crystal clear, crystal set,