Which is true about scientific theories?

a: they are the result of a single experiment.
b: they are the results of many experiments over a long period of time.
c: they are proposed by scientists who wish to investigate a new topic.
d: they are only based on the most recent evidence.

they are results of many experiments over a long period of time

the earths atmosphere is made up of nitrogen and oxygen. solids can turn into gasses through a process called sublimation. sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

hope this : d