arduous

adj. 费力的,辛勤的,险峻的

archduke, archer, archery, archetypal, archetypally, archetype, archipelago, architect, architectural, architecture, archive, archives, archivist, archway, Arctic, Arctic Circle, ardent, ardently, ardor, ardour (US ardor), arduously, are, area, area code (US) dialling code, areca, areca nut (also betel-nut), aren't, arena, arete, argon, argot, arguable, arguably, argue, argument, argumentation, argumentative, argumentatively, argy-bargy, aria,