例句與造句

1. The mountain ridges of the south are composed of old red sandstone separated by limestone river valleys
   南部地區(qū)的山脊由古老的紅砂巖組成，中間被石灰?guī)r的河谷分離。
2. It's difficult to find old red sandstone in a sentence. 用old red sandstone造句挺難的