Answer:
Gamma Rays
Step-by-step explanation:
Gamma rays are the highest penetrating power. It is emitted from the nucleus of a radioactive atom during radioactive decaying. They are capable of travelling many yards in air. Gamma rays can easily penetrate a human body. Shielding this very high penetrating type of ionizing radiation requires a thick dense material such as several inches of concrete or lead.
Thus, gamma rays is the most penetrating and can pass through several layers of concrete shielding.