A 300 mm square bearing plate settles by 15 mm in a plate load test on a cohesive soil when the intensity of loading is 0.2 N/mm2. The settlement of a prototype shallow footing 1 m square under the same intensity of loading is A. 15 mm B. 30 mm C. 50 mm D. 167 mm

The correct answer is $\boxed{\text{B) 30 mm}}$.

The settlement of a footing is proportional to the square of the footing width and the intensity of loading, and inversely proportional to the undrained shear strength of the soil. In this case, the footing width is increased by a factor of 3.33 (from 300 mm to 1 m), but the intensity of loading is kept the same. Therefore, the settlement of the prototype footing is expected to be 3.33 times the settlement of the test plate, or 30 mm.

Option A is incorrect because it is the settlement of the test plate. Option C is incorrect because it is twice the settlement of the test plate. Option D is incorrect because it is much greater than the settlement of the test plate.