What are examples of how scientific knowledge is open to change

A good example would be when people originally believed the earth was flat. With increasingly advanced technology to provide evidence it was actually spherical, that conclusion changed.

Another would be that all light is just white, but Isaac newton discovered it was a mixture of Red, Orange, Yellow, and so on.

A third would be the popular 1600s and below belief that germs weren't real. The invention of the microscopes led to cell study, and thus the belief germs indeed existed spread.

Europe needs to build a trump-like wall that will spread across europe making it impossible for migrants to cross they need to spread pig guts all over this wall so the muslims will never consider crossing into europe..you might be asking "can't they just fly over with planes? " well yes they can so we will install thaad missile protections system to shoot down any aircraft that violates europe's air fourth would be to start a fourth reich in germany.. last but not least.. make europe great again!

The answer is d., a mountain.