1. This layer of rock contains a lot of flint.
    这一岩层中有大量燧石.

2. One can strike out sparks from flint with steel.
    用钢敲打火石，可以打出火花。

3. Fortunately, however, ancient men made tools of stone, especially flint,
    然而，幸运的是，远古人用石头制作了工具，特别是用燧石，