下表代表寒潮、酸雨、水土流失、土地荒漠化对四省区的危害程度(●越多代表程度越高),回答题。
| 甲 | 乙 | 丙 | 丁 | |
| 广东 | ●● | ● | ●● | ●●●● |
| 四川 | ●●● | ● | ● | ●●● |
| 新疆 | ● | ●● | ●●●● | |
| 山西 | ●●●● | ●●● | ● | ● |