What does it mean when you see a nucleus in a cell ?

idk i’m struggling too

i'm assuming that the correct answer is indeed the first one/ "a"..

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8