What skills from the following refer to the manager's ability to prioritize work, to work efficiently, and to delegate appropriately?

Correct option is D - time management.
Time management is the skill managers rely on to be able to prioritize work, to work efficiently and to delegate appropriately.

Conceptual skill is the skill managers use to think in the abstract.
Interpersonal skill is the ability to communicate, understand and motivate individuals within and outside an organization.

Technical skill is use to accomplish or understand the specific kind of work done in an organization.
Decision making skill is the ability to recognize and define problems and opportunities and then to select a course of action to solve problems and capitalize opportunities.