If a is the offset of concrete bed in cms, and d is the depth of concrete bed in cms, then

Answer: Option B

The relationship between the offset (a) and depth (d) of a concrete bed comes from the standard slope provided for bed concrete in foundations.

In practice, the concrete bed is laid with side slopes of approximately 63° 26′.

Using this slope, the ratio between depth (d) and offset (a) becomes:

d = a × tan(26° 34′) ≈ 0.557 a

Thus, the correct proportional relationship between depth and offset of a concrete bed is:

d = 0.557 a