Answer:
O(Oxygen)
Step-by-step explanation:
Oxygen or O among the given options has the highest electronegativity of 3.5 as compared to 2.4 of sulfur. Thus, there is a lesser attraction in the bonds of Sulfur. The other two elements Al(Aluminium) and Cu are less electronegative than Sulfur and Oxygen as they are metals and possess electropositivity while the latter displays more electronegativity due to being non-metals. Hence, Oxygen is the answer.