cave-in

n sudden collapse of a roof, etc （屋顶等）突然坍塌.

causation, causative, cause, causeway, caustic, caustic soda, caustically, cauterize, cauterize, cauterise, caution, cautionary, cautious, cautiously, cautiousness, cavalcade, cavalier, cavalry, cave, cave in, cave-dweller, caveat, caveman, cavern, cavernous, caviare (also caviar), cavil, cavity, cavity wall, cavort, caw, cayenne, cayman (also caiman), CB, CBC, CBE, CBI, CBS, cc, CD, CD-ROM,