The correct answer is: "open their own businesses
".
In a mixed market economy, economic authorities implement income redistribution systems that reduce income inequalities and generate fairer outcomes for all the individuals that conform the society, if compared to the results that would be generated by the free interaction of economic agents in the markets (pure market economy situation).
Therefore, agents can choose their path (for example, open a business), but they do not lead the economy on their own, through their choices, because the effects of those choices are subsequently modified by the regulation of the goverment. Economic authorities keep an eye in the functioning of all markets and, therefore, on the forces of demand and supply.