A project manager is responsible for all that goes on in the project. One of the most important duties that the project manage can perform is the function of:

............. d. Integration................

Option D appears to be correct as it encompasses all the activities concerned for the project.

Otherwise each and every aspect of other options are important for Project Manager.

Answer is  D

Since the project manager is responsible for a temporary multifunctional team of people who are brought together for the purpose of one project it is most important that the project manager perform the function of integration.

Certainly integration,

As we know, at least a project manager should plan and control 9 knowledge areas 

Scope, time, cost, quality, HR, risk, communication, procurement and stakeholders management and PM is allowed and authorized to delegate each knowledge area, only knowledge area that PM have to manage it directly is integration management

My opinion is the answer is:

d. Integration

I fully endorse answer given by Mr. Mohammed Helal. Thanks.

Option D cover a,b and optioin c. ........

Integration is the good answer

thanks for invition ,,,,,,,,,, my choice is option D

A cooling tower is a heat exchanger, inside of which heat is withdrawn from the water by contact between the water and the air. The heat transfer occurs through the heat exchange between air and water and through the evaporation of a small part of the water that needs to be cooled

Of course function of any manager is Intergration. Hence D is the right answer