challenging

a.挑战的；引起争论的

chain-smoke, chain-smoker, chain-stitch, chain-store, chair, chair-lift, chairman, chairperson, chairwoman, chaise longue, chalet, chalice, chalk, chalk-mark, chalkboard, chalkiness, chalky, challenge, challenged, challenger, chamber, chamber concert, chamber music, chamber of commerce, chamber of horrors, chamber orchestra, chamber-pot, chamberlain, chambermaid, chameleon, chamois, chamomile, champ, champagne, champion, championship, chance, chancel, chancellery, chancellor,