'House' is related to 'Foundation' in the same way as 'Tree' is related too '________'.

Root

'House' is related to 'Foundation' in the same way as 'Tree' is related too '________'.

The logic followed here is:

Foundation is the layer of bricks etc. under the surface of ground that forms the solid base of a building or house

Similarly

Root is the part of plant or tree that grows under the ground and takes in water and food from the soil