user: What country has the highest GDP?

assistant: The United States has the world's largest GDP at market rate exchange rates.  The United States also accounts for approximately 25% of the global GDP.  It is the largest importer and second-largest exporter.  Having only 4.2% of the world's population, the United States holds over 30% of the total wealth in the world, which is the largest share held by one country.

user: What is the Sun?

assistant: The sun is how we refer to the star in our solar system, around which each of the planets rotate.

user: When should I take vitamin D?

assistant: If you live in England, NHS recommends that people with vitamin D deficiency take supplements, other people should get vitamin D directly from the sun from April to September and take a supplement containing 10 μg (400 IU) of vitamin D during autumn and winter.