World News from the BBC. President Barack Obama has arrived in Costa Rica to attend the summit of Central American leaders and discuss ways of tackling the increasing violence generated by drug cartels operating in the area. ______________A plane powered only by the Sun has set off from San Francisco on the first leg of a journey across the United States. It's being piloted by Bertrand Piccard, who was the first person to circumnavigate the globe in a hot-air balloon in 1999. Martin Vennard has more. 这里是BBC 世界新闻.美国总统巴拉克?奥巴马抵达哥斯达黎加出席中美洲领导人峰会,商讨如何应对此地贩毒集团所引发的日益猖獗的暴力事件._________________一架仅以太阳能为动力的飞机从旧金山启程,这是其环美之旅的首站.驾机者名叫伯特兰 ? 皮卡德,他曾在1999年乘坐热气球完成环球旅行,成为业内第一人.马丁?文那德将带来详细报道.
