I need help.. kinda hard but alot points will give brainliest

Which of the following is true of photosynthesis? a)carbon dioxide is a reactant b)water is a product c)most reactions within this process are exothermic d)oxygen is a reactant

Which best explains why there are 64 possible codons in the genetic code and only 20 amino acids that make protiens of living organisms on earth

What is thought to have caused the mass extinction at the end of the cretaceous period?