A control group in a scientific experiment is a group separated from the rest of the experiment, where the independent variable being tested cannot influence the results. This isolates the independent variable 's effects on the experiment and can help rule out alternative explanations of the experimental results.
it’s B (because 20 Is smaller than 50)
An ignious rock's color is mainly determined by its silica content
The answer is c to take a pictures with the camera in the metal hall