This table shows statistics about the US population in 2010.

US Population by Age Group (2010)

\begin{tabular}{|l|l|l|}
\hline Age Group & \begin{tabular}{l}
Percent of \\
Population
\end{tabular} & \begin{tabular}{l}
Total \\
Number
\end{tabular} \\
\hline Under 18 & [tex]$24.0 \%$[/tex] & [tex]$74,181,467$[/tex] \\
\hline [tex]$18-24$[/tex] & [tex]$9.9 \%$[/tex] & [tex]$30,672,088$[/tex] \\
\hline [tex]$25-44$[/tex] & [tex]$26.6 \%$[/tex] & [tex]$82,134,554$[/tex] \\
\hline [tex]$45-64$[/tex] & [tex]$26.4 \%$[/tex] & [tex]$81,489,445$[/tex] \\
\hline \begin{tabular}{l}
65 and \\
older
\end{tabular} & [tex]$13.0 \%$[/tex] & [tex]$40,267,984$[/tex] \\
\hline
\end{tabular}

Which demographic trend does this table best support?

A. People are marrying later than they used to.
B. There are more single-parent families.
C. The American population is more diverse.
D. There are fewer younger adults than older adults.

To determine which demographic trend is best supported by the statistics provided for the US population in 2010, let's analyze the given percentages for different age groups:

- Under 18: 24.0%
- 18-24: 9.9%
- 25-44: 26.6%
- 45-64: 26.4%
- 65 and older: 13.0%

We are asked to compare the percentage of younger adults, specifically aged 18-24, with the percentage of older adults, 65 and older.

From the data:
- Percentage of the population aged 18-24: 9.9%
- Percentage of the population aged 65 and older: 13.0%

When we compare these two percentages, we see that 9.9% (younger adults) is less than 13.0% (older adults).

Therefore, the data shows that there are fewer younger adults (aged 18-24) than older adults (aged 65 and older).

Given the options provided:
- People are marrying later than they used to.
- There are more single-parent families.
- The American population is more diverse.
- There are fewer younger adults than older adults.

The correct trend that this table best supports, based on the comparison of age groups, is:
There are fewer younger adults than older adults.