How are window functions different from regular aggregate functions?

How are window functions different from regular aggregate functions?
A . Rows retain their separate identities and the window function can access more than the current row.
B . Rows are grouped into an output row and the window function can access more than the current row.
C . Rows retain their separate identities and the window function can only access the current row.
D . Rows are grouped into an output row and the window function can only access the current row.

Answer: A