When an Alpha Particle Hits A ${ } _ { 19 } ^ { 39 } \mathrm {~K}$

When an alpha particle hits a ${ } _ { 19 } ^ { 39 } \mathrm {~K}$
Nucleus,one of the products is a proton.The other product is

A) ${ } _ { 18 } ^ { 36 } \mathrm { Ar }$
B) ${ } _ { 17 } ^ { 38 } \mathrm { Cl }$
C) ${ } _ { 20 } ^ { 42 } \mathrm { Ca }$
D) none of these.