ANS:E - none of these.

The selection of "none of these" as the answer indicates that none of the provided options are incorrect or applicable to the question. In this case, the question asks for the incorrect size of stone ware sewers, but none of the sizes listed (52.5 cm, 67.5 cm, 82.5 cm, and 90 cm) are deemed incorrect. Therefore, by choosing "none of these," it is implied that all the sizes mentioned are valid and correct for stone ware sewers. This suggests that there is no incorrect size among the options provided, and the correct size may not be listed among the options.