Answer:
A. God sent many plaques to Egypt
First of all, you dont have the answers.
But the answer is "Companies replaced hand-operated brakes with air brakes on trains" is the best answer because this stopped many of the fatalities that were caused by brake failures." which is I say on what you are using D
Answer: Option 'a' is correct.
Explanation:
Researchers can isolate a single factor and examine the effect of that factor alone on a particular behavior through use of a choices is an experiment.
As experiment means when a hypothesis is tested scientifically and check when the cause is changed what would effect that factor alone.
whereas correlational study is the study of two variables understand it and develop the statistical relationship between them without affecting from any variable.
Hence, option 'a' is correct.
