Question $23$

$2\mathrm{.}5$ pts

The spontaneous emission of an alpha particle by $239$Pu can be represented by ${?}^{239}Pu4He+{?}^{235}U.$ A check of the masses of the products would reveal that

a$.$ the sum of the masses of $4$ He and ${?}^{235}U$ is greater than the mass of ${?}^{239}Pu.$

b$.$ there is no change in the mass during the transformation.

c$.$ the sum of the masses of $4$ He and ${?}^{235}U$ is less than the mass of ${?}^{239}Pu.$

d$.$ the mass of ${?}^{239}Pu$ equals the mass of ${?}^{235}U.$

e$.$ the alpha particle, like a photon, has no mass.