Option D: Electrically operated machines are preferable to use.
     ● Statement 1: All machines consume energy.  
       This statement establishes that machines require energy to function, but it does not specify the type of energy.
     ● Statement 2: Electricity provides energy.  
       This statement indicates that electricity is a source of energy, but it does not imply that it is the only source.
     ● Statement 3: Electrically operated machines are cheap to maintain.  
       This suggests a cost advantage of using electrically operated machines.
     ● Statement 4: Electrically operated machines do not cause pollution.  
       This implies an environmental benefit of using electrically operated machines.
     Analysis of Options:
     ● Option A: All machines are run by electric energy.  
       This cannot be inferred because the statements do not claim that all machines use electric energy; they only highlight the benefits of electrically operated machines.
     ● Option B: There is no form of energy other than electricity.  
       This is incorrect as the statements do not exclude other forms of energy; they only mention electricity as a source.
     ● Option C: Most machines are operated on electric energy.  
       This cannot be concluded from the given statements as they do not provide information about the proportion of machines using electric energy.
     ● Option D: Electrically operated machines are preferable to use.  
       This is the most logical inference based on the given statements. The advantages mentioned in statements 3 and 4 (cost-effectiveness and lack of pollution) suggest that electrically operated machines are preferable.
     Therefore, the correct inference is that electrically operated machines are preferable to use, making Option D the correct answer.