Shielding Is an Important Aspect of Working with Radioactive Materials $\alpha$

Shielding is an important aspect of working with radioactive materials. Which of the following is the order of radiation type in order of increasing penetration?

A) $\alpha$ , $\beta$ , $\gamma$
B) $\beta$ $\alpha$ , $\gamma$
C) $\gamma$ , $\beta$ , $\alpha$
D) $\beta$ , $\gamma$ , $\alpha$
E) $\alpha$ , $\gamma$ , $\beta$