\begin{tabular}{|c|c|c|}
\hline
\multicolumn{3}{|c|}{
\begin{tabular}{l}
Citizen Participation in Wartime Activities in the US \\
(Millions of Citizens)
\end{tabular}
} \\
\hline
\begin{tabular}{l}
Type of \\ participation
\end{tabular} & 1916 & 1919 \\
\hline
Active military & 0.18 & 1.27 \\
\hline
\begin{tabular}{l}
Total number \\ of employed \\ workers
\end{tabular} & 40.1 & 42.3 \\
\hline
\end{tabular}

What does the chart indicate about American employment during World War I?

A. The number of people in the armed forces increased by more than one million.

B. The number of people in the workforce increased by about three million.

C. The number of people in the armed forces declined by one million.

D. The number of people in the workforce declined by one million.

To determine the changes in the number of people in the armed forces and the workforce in the US during World War I based on the given chart, let's break down the information step by step.

### Data Given
From the chart, we have the following information:

1. Active Military:
- In 1916: 0.18 million people
- In 1919: 1.27 million people

2. Total Number of Employed Workers:
- In 1916: 40.1 million people
- In 1919: 42.3 million people

### Changes in Numbers
Now, let's calculate the changes:

1. Change in the Number of People in the Armed Forces:
- The number of active military in 1919 is 1.27 million.
- The number of active military in 1916 is 0.18 million.
- Change = 1.27 million (1919) - 0.18 million (1916)
- Change = 1.09 million

2. Change in the Number of Employed Workers:
- The total number of employed workers in 1919 is 42.3 million.
- The total number of employed workers in 1916 is 40.1 million.
- Change = 42.3 million (1919) - 40.1 million (1916)
- Change = 2.2 million

### Interpretation of the Changes
Based on the calculated changes, we can interpret the statements given:

1. The number of people in the armed forces increased by more than one million.
- The increase was 1.09 million, which is indeed more than one million. This statement is correct.

2. The number of people in the workforce increased by about three million.
- The increase was 2.2 million. While it is an increase, it is closer to two million rather than three million. This statement is incorrect.

3. The number of people in the armed forces declined by one million.
- This is incorrect, as there was an increase, not a decline. This statement is incorrect.

4. The number of people in the workforce declined by one million.
- This is incorrect, as there was an increase of 2.2 million in the workforce. This statement is incorrect.

### Conclusion
The correct insight from the chart is that the number of people in the armed forces increased by more than one million, and the number of people in the workforce increased by about two million. The statement that accurately reflects the data from the chart is:

- The number of people in the armed forces increased by more than one million.