Meteorology.
A meteorologist uses science to learn and understand a certain part of Earth's atmosphere, and uses that knowledge to predict weather patterns and how they will impact Earth's systems.
he correct answer is -NATIONS-
The correct answer is "source" - this is the beginning of the river. (typically in the mountains)
Mouth of a river is the "end" of the river- it's when the river joins the ocean.
A tributary is another river that ends in the main river
and the watershed is a piece of land that separates bodies of water.
The astrometric method is searching for tiny wobbles in the position of the star due to the gravitational pull of a planet orbiting around it.
I hope this helps
