Answer:
Option D, Four.
Step-by-step explanation:
A carbon atom has four electron in its outermost shell. Thus in order to complete its octate (which has 8 electrons) a carbon needs to form four bonds. Thus a carbon can bond with either 4 other atoms or molecules.
For example -
CH4
Carbon has 4 electron in its outermost shell. Four more electrons are donated by hydrogen atom with each hydrogen atom fulfilling one valency of carbon. Thus now carbon has 8 electron in its outermost shell.
Thus, option D is correct.