The correct option is A 2,1
Atomic number of an atom is equal to the number of protons in an atom. For a neutral atom, the number of protons is equal to the number electrons.
The innermost shell of an atom can accommodate a maximum of two electrons and the second shell can accommodate a maximum of eight electrons.
Atomic number of lithium (Li) is 3. Hence, lithium has 3 electrons and its electronic configuration is 2,1.