The best way for a government to improve the standard of living in its country from the given options is:
C. invest in the education of children and adults in the country
Investing in education generally leads to a more skilled workforce, higher productivity, and better job opportunities, which can contribute to overall economic growth and improved living standards. Education also fosters innovation and helps to reduce inequality, which can have long-term positive effects on society. The other options could result in negative consequences, such as economic isolation or conflict, which would likely harm rather than help the standard of living.