Hello there!
Your question asks which organization, in the United States, studies and assesses the environment to protect it.
Answer: United States Environmental Protection Agency
The reason why the United States Environmental Protection Agency is the correct answer is because that tis the specific organization that makes sure that the environment is protected, and that people importantly are protected if there is a negative change in the environment.
The United States Environmental Protection Agency is a federal agency for the government, and was founded during the year of 1970. The reason the government made this agency is so that the environment in the country is protected. The person who founded this agency was President Richard Nixon. This agency is appointed by the President, along with being approved by Congress. This agency specifically looks at things that are causing the negative affects in the environment like: pollutants, chemicals, plantations, etc. Because they examined those things, they try to make sure that the health of someone is protected by making restrictions or limitations to those. For example, factories are only allowed to pollute a certain amount of CO2 in the air.
I hope this helped you out!