Concept:Different radiations have different penetrating powers: alpha is the least penetrating, while gamma is the most penetrating.
Explanation:Alpha particles are very weakly penetrating.
They are easily stopped by paper or a thin aluminum foil.
Beta particles can pass through paper, but a few millimetres of aluminum sheet absorbs them.
Gamma rays are highly penetrating and pass straight through aluminum foil.
Gamma rays can only be reduced significantly by dense materials such as lead or thick concrete.
Therefore, aluminum foil blocks both alpha and beta particles but not gamma rays.
Answer:A. alpha and beta particles