To answer the first part of your question, I'd like to say that our studies were very extensive.
你问题的第一部分,我要说的就是我们的研究非常广泛。
If there had not been a hard layer of rock beneath the soil, they would have completed the job in a few hours.
如果不是因为土壤下面有一层坚硬的岩石,他们的营救工作仅用几个小时就可以完成了。