A homogeneous mixture is a mixture that is mixed so well together that you cannot see the different components that make up the mixture as the ingredients will not separate out, even over time.
Probably life science or biology.
B, radon is correct. Interestingly, it often collects in basements from radioactive decay of rocks such as granite that contain uranium. Because it is an unreactive noble gas and because it is denser than air it sits in basements and must be pumped out. It collects in human lungs and is the second leading cause of lung cancer behind smoking.
Moving the electron away from the nucleus requires energy, so the electrons in the outer shell will have more energy than ones in the inner shell. Electrons always have a charge of -1, so the charge in the inner and outer shell will be the same. Therefore the answer is 3
