Step 1: Understanding management objectives. 
  
In management, achieving objectives requires a combination of efficiency and effectiveness. Efficiency refers to achieving tasks with the least amount of resources, while effectiveness involves completing tasks that align with organizational goals. A manager needs both efficiency and effectiveness to successfully meet objectives. 
Step 2: Analyzing the options. 
  
(A) Through efficiency: Incorrect. While efficiency is important, it alone may not be sufficient to achieve the full objectives of an organization. 
  
(B) Through effectiveness: Incorrect. Effectiveness is essential, but achieving objectives also requires efficiency in utilizing resources. 
  
(C) Through efficiency and effectiveness: Correct. The combination of both efficiency and effectiveness is key to achieving organizational objectives. 
  
(D) None of these: Incorrect. The correct answer is (C). 
Step 3: Conclusion. 
  
A manager achieves objectives through a combination of efficiency and effectiveness. Thus, the correct answer is (C).