For about how many years of geological time have humans existed on earth?

Liquid water turns into water vapor at which step in the water cycle? a. precipitation o b. water run off c. evaporation d. condensation

(drag each tile to the correct identify which questions can be answered by what can be answered by science or which cannot. -is it right or wrong to use genetic engineering to produce new food products? -what are the most common social settings that tend to produce accomplished artists? -if a new gene is added to the genome of a tomato species, will that species be more resistant to insects? -should humans use biotechnology to bring extinct organisms from the fossil record back to life? -do the types of organisms found in the fossil record appear in consistent sequences in different parts of the world? -are michelangelo's paintings more impressive than rembrandt's?

Nh3 +02-no + h20 is unbalanced what is the balanced equation