The correct answer is D. All of the above.
Rotary drilling is a method of drilling that uses a rotating bit to cut through the earth. It is a very versatile method of drilling and can be used for a variety of applications, including water well drilling, oil and gas exploration, and mining. However, rotary drilling has some limitations.
One limitation of rotary drilling is that it is not suitable for deposits containing very coarse gravel. The rotating bit can become clogged with the gravel, making it difficult to drill through the material.
Another limitation of rotary drilling is that it can hinder groundwater observations and permeability tests. The drilling process can create a disturbance in the ground, which can make it difficult to accurately measure groundwater levels and permeability.
Finally, rotary drilling is not economical for holes of less than 10 cm. The cost of drilling a small hole is relatively high, and the benefits of doing so may not outweigh the costs.
In conclusion, rotary drilling is a versatile method of drilling with some limitations. It is not suitable for deposits containing very coarse gravel, it can hinder groundwater observations and permeability tests, and it is not economical for holes of less than 10 cm.