Which one of the 4 is the answer

Its neither

Step-by-step explanation:

Since the area of the floor is 100 and one side is 10, then we should know that the other side is 10 because, 
10 * 10 = 100

So, since two sides are 10, than the other sides must be 10 too.

That gives 4 sides that all equal 10.

10+10+10+10= 40

So, the perimeter is 40.