i mark the option D) but answer is A)
A) f(n)=Ω(nlogn) means f(n)>=c* nlogn
D) f(n)=O(nlogn) means f(n)<=c* nlogn which means that no comparison based algo takes more than nlogn time. But we know there are algo like bubble sort, worst case of quick sort etc that takes n2 time which is more than nlogn. That is why option A.