The Nuclei Of ${ } _ { 2 } ^ { 4 } \mathrm { He }$

The nuclei of ${ } _ { 2 } ^ { 4 } \mathrm { He }$ are also known as

A) $\alpha$ particles.
B) positrons.
C) $\beta$ particles.
D) x-rays.
E) $\gamma$ rays.