First nuclear reactor was built in

Options

A. Russia
B. U.S.A
C. U.K.
D. France

Answer

To answer the question about where the first nuclear reactor was built, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Question**: The question asks where the first nuclear reactor was built.

2. **Recall the Name of the Reactor**: The first nuclear reactor is known as "Chicago Pile-1".

3. **Know the Scientist Involved**: The reactor was built by the renowned scientist Enrico Fermi.

4. **Determine the Year of Construction**: Chicago Pile-1 was constructed in the year 1942.

5. **Locate the Construction Site**: The reactor was built underneath the University of Chicago.

6. **Identify the Country**: Since the University of Chicago is located in the USA, we can conclude that the first nuclear reactor was built in the USA.

7. **Select the Correct Option**: Based on the information gathered, the correct answer is the USA.

### Final Answer:
The first nuclear reactor, Chicago Pile-1, was built in the USA in 1942.

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