Answer: The correct answer is 4.
Explanation-
The atomic number of carbon is 6. Its electronic configuration is 2,4
The electronic configuration depicts that k shell of the carbon atom contains 2 electrons. The outer shell or the valence shell contains 4 electrons.
Every atom wants to possess 8 electrons in its valence shell in order to become stable.
Thus, the number of electrons lacked by carbon atom = 8-4
= 4