One challenge of socialism that both socialists and capitalists would agree on is
a. the high cost of socialist objectives.
b. its bureaucratic nature.
c. the role of central planners.
d. its emphasis on individual freedom.

The answer is c. the role of central planners. Even though they are different, the success of an economic system will depend on the central planners.  How well they implement their economic policies and how many benefit will determine whether or not their plans and programs are a success.

the secretary of defense is the principal defense policy advisor to the president. under the direction of the president, the secretary exercises authority, direction, and control over the department of defense.

as you did not provide any choices for me to choose from to give you a direct answer, this is the only information i can provide.