How did the development of canals and dams affect Chinese farmers? O They were able to plant crops that needed less water to grow.
O They had to take time from farming to maintain the structures.
O They ran short of labor because workers went to build canals and dams.
They could grow more crops because their water supply was controlled.

The development of canals and dams meant for the Chinese farmers that they could grow more crops because their water supply was controlled.

Explanation:

The first option is not correct because the crops did not just change to produce the same amount but require less water.

The second option is not correct because there is an abundance of people (thus labor force) in China, so the farmers didn't have to stop farming and maintain the structures.

The third option is not correct because China has the largest labor force in the world, so the farmers didn't have problems with the labor force for their farms.

The fourth option is correct because once the water supply was controlled, the farmers had water when they needed for their crops, not like before that when they were experiencing periods of drought or massive floods.

doctrine that the us had the right to expand throughout north america.