Tolong bantu jawab yaa ^-^

Aku bantu PG aja ya ^-^

[1.]Neutron = nomor massa - nomor atom
=>19 - 9 =10 (C)

[2.]
[tex] ^{39}_{19} K [/tex]
C. 19 proton,20 neutron, 19 elektron

[3.] D. [tex] ^{127}_{53} A [/tex]