《生存之旅》（Left4Dead）将于美国时间4月27日放出最新扩充包《生存之旅：
B-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game I-game O O O O O O O O O O O O O O O O O O O O O O O O