oil-bearing grade

例句：

1. 1. The oil-bearing rock is the key to unlocking the ancient city's secrets.
   含油岩石是解锁古老城市秘密的关键。
2. 2.The oil-bearing region has been a hotspot for oil exploration.
   含油地区一直是石油勘探的热点。
3. 3. The oil-bearing grade of this oil is high, which means it can be used for industrial purposes.
   这种油的含油等级很高，这意味着它可以用于工业用途。