challenge

n.挑战；艰巨任务；向…挑战；对…表示怀疑

chain-letter, chain-mail, chain-saw, chain-smoke, chain-smoker, chain-stitch, chain-store, chair, chair-lift, chairman, chairperson, chairwoman, chaise longue, chalet, chalice, chalk, chalk-mark, chalkboard, chalkiness, chalky, challenged, challenger, challenging, 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,