What causes high pressure systems?
rainfall hyperthyroidism heating liquids mechanical chemical changes sinking air fossil fuels our nearest star
A B C D E F G H
Clear weather is caused by sinking air.
High pressure systems are the result of sinking air. 
What causes high pressure systems? (A) rainfall (B) hyperthyroidism (C) heating liquids (D) mechanical (E) chemical changes (F) sinking air (G) fossil fuels (H) our nearest star