我们在胡杨林边安营扎寨，列车靠在一棵树冠足有篮球场大的胡杨树。
B-Person I-Person O B-Location I-Location I-Location I-Location O B-Thing O B-Thing O B-Thing I-Thing O O B-Metric I-Metric B-Location I-Location O O B-Thing I-Thing I-Thing O O B-Thing I-Thing I-Thing O