How did the invention of hydraulic mining allow for larger mining operations?

a. air blown at high pressure could remove unwanted materials from steel.

b. water released at high pressure could move large rocks out of the way.

c. new tools were better able to cut through shallow grass and rocks in the soil.

d. wind power could be used to pump water and produce electricity.

The correct answer is letter "B".

The invention of hydraulic mining allow for larger mining operations since water released at high pressure could move large rocks out of the way.

Explanation:

This technique use water cannons that allows water come out with a lot of pressure. These "water cannons" are very powerful since they can throw thousands of cubic feet of water in an hour with a high speed per second. This procedure allows to drag tons of rocks, gravel, earth. The material to be removed is suspended in the water. This allows it to be washed until the collection stage.

It is also a technique that has been highly questioned because of the great negative environmental impact.

your list doesn't mention any of them at all.

and what does "these" mean anyway ?

one of the negative side effects were the economic losses the events of september 11th caused. many, many people lost their jobs as a result of a downturn in the economy after the terrorist attacks.