Why are lager astronomical bodies such as planets and stars round?

Gravity pulls mass towards its center, therefore as matter is pulled towards a source of gravity it will naturally coalesce into a ball as matter competes to head towards the source of gravity.

They are around because of the Big Bang Theory

Answer(2) electrons;

Answer is: hydrogen is being oxidized.chemical reaction: co₂ + h₂ → co + h₂o.oxidation half reaction: h₂ → 2h⁺ + 2e⁻.reduction half reaction: c⁺⁴ + 2e⁻ → c⁺².oxidation is increase of oxidation number, hydrogen change oxidation number from neutral charge (in molecule of hydrogen) to oxidation number +1 (in water).