Why is oxygen more expensive than silicon, aluminium, iron, calcium, sodium, potassium, magnesium?

The passing of heat through a material while the material itself stays in place. a. radiation b. conduction c. convection

If gases like carbon dioxide and methane make up less than 1% of the total atmosphere, why is it important for scientists to monitor changes in percentages of these gases?

Apair of 10μf capacitors in a high-power laser are charged to 1.7 kv.a. what charge is stored in each capacitor? b. how much energy is stored in each capacitor?