Answer:
The correct option is 2.
Explanation:
Greatest integer function is defined as

where, n is an integer.
Least integer function is defined as

From the given graph it is clear that it is a graph of greatest integer function because the we have open circles on the right side of each floor and closed circle on the left side of each floor.
The given graph is defined as

Graph of greatest integer function shifts 2 units up.

Therefore the correct option is 2.