In a unitary system of government, power is a) held by state governments. b) held by a central government. c) held by a single person. d) held by a group of people.

The correct answer is B.

A unitary system of goverment is constituted by a central goverment with unlimited powers, as there is no power division, and power is only delegated to subordinated units if the goverment decides to do so. In any case, the actions of these subordinates can be abolish or vetoed by the supreme government.

Alternatively, in most modern democracies, division of powers exists and divides the power of the state in three branches: legislative, executive and judiciary.  

could you give me the options ?

b.

one company controls all the means of production of a product.

~coco