You are presented with the question "What do high pressure systems allow?" and the following answer choices: 
- water conservation
 - Veins and arteries.
 - hydrogen and oxygen
 - Animal survival
 - to move people
 - heat energy
 - heating liquids
 - sailplanes to fly

Now knowing that high pressure systems cause clear weather and sailplanes fly in clear weather, choose the best answer.


 

        sailplanes to fly 