Answer:
B
Explanation:
Most experiments require a control group AND one experimental group.
Answer:
C) having other scientists repeat your results
Explanation:
The fact that other scientists repeat an experiment will increase the validity of it, since the probability of an error will be lower due to a bad measured coming from a single scientist.
For example, in the release of the first image of a black hole. Some different groups of scientists treated the data using different methods to get that image, and all of them reached the same result.
