Topic: Linkers or Connectors,

Best Answer Explained in Below-:

In the sentence "He can stay --- he wants," the correct completion is "as long as" (option C). This phrase is commonly used in English to indicate a conditional relationship, suggesting that the length of time someone can stay is dependent on their desire or willingness. The structure implies that his ability to remain is directly linked to how much he wants to stay.

Option A, "as longer as," is incorrect because "longer" is a comparative form that does not fit grammatically in this context; it should be just "long." Option B, "as lengthy as," is awkward and not commonly used in everyday speech when referring to time, making it less suitable. Option D, "as long," can be used, but it changes the meaning slightly—the phrase would imply a more fixed quantity of time without the conditional aspect inherent in "as long as."

Thus, "as long as" effectively communicates the idea that his stay is contingent upon his desire, making it the most applicable choice in this context.