S1 : merge sort on linked list take O(nlogn)
S2: If we talk about Extra space then, in array it is O(n) and in case of linked list it is O(logn) . So, linked list have less space complexity.
S3: Inplace algo recurrence relation :
2T(n/2) +n²= O(n²)
So, S1, S2, S3 all are correct