Answer:
B. the smallest cost slope on the CP
Explanation: CPM(critical path method) is a framework in project management, which involves a step wise approach to planning of a project in order to determine the which path or which process or steps in the project requires to given more time, what path or portion of the projects needs to be analysed or reviews for further improvements.
TO REDUCE THE DURATION OF A PROJECT USING CPM, IT IS EXPECTED THAT THE ACTIVITY WITH THE SMALLEST COST SLOPE ON THE CP IS REDUCED.