Which of the following is true about scientific theories? i. new research is often done to learn more about existing scientific theories. ii. scientific theories can be revised, changed, or even rejected. iii. scientific theories are considered to be facts and cannot ever be modified. iv. new scientific theories can be formed to explain new phenomena.

Well surely 1, 2 and 4 are true, e.g, it was once thought that earth was the centre of the universe, this was revised and rejected. Scientists are still researching the existence of the universe using more advanced technology to test old theories. There are also new phenomena in which cannot be explained but there are theories to suggest why. But 3 is completely wrong as they are not treated as facts but a prediction until proven. 

Idkk take a guess i am no