Option D: Television is not a luxury item.
     ● Statement Analysis: The given statement is "Though quite expensive, television is not a luxury item, as one can learn many things through television." This statement suggests that despite the high cost, television is not considered a luxury because it serves an educational purpose.  
     ● Option Analysis:  
       ● Option A: "All expensive things are regarded as luxury." This is not a valid inference because the statement explicitly mentions that television, despite being expensive, is not a luxury item. Therefore, not all expensive things are regarded as luxury.  
       ● Option B: "All essential things for learning are not luxury." The statement does not provide enough information to generalize about all essential learning tools. It only discusses television specifically.  
       ● Option C: "Television is essential for learning." The statement does not claim that television is essential for learning, only that it is a medium through which one can learn many things.  
       ● Option D: "Television is not a luxury item." This directly aligns with the statement provided, which explicitly states that television is not a luxury item.  
     ● Conclusion: Based on the analysis, the valid inference from the statement is that television is not a luxury item, making Option D the correct answer.