Who answers the questions in a centrally planned economy?

Typically, a person who knows the answer will answer a question put to him and being in a centrally planned economy has nothing to do with it.

If the question intends to ask "Who makes the decisions of how much to produce in a centrally planned economy?" the answer to that would be, generally speaking, the government, and specifically it would be an economics ministry of the state. In the Soviet Union, for example, there was the State Planning Committee, popularly known as Gosplan, that made key decisions in terms of how much to produce in all major industries.