ANS:D - none of these.

1. Heap: A heap typically refers to a pile of objects or materials stacked in a disorderly or random manner. While vegetable wastes and night soil could indeed be piled in a heap, the specific method described in the question involves layering them alternately to form a mound, which suggests a more structured approach than a heap.
2. Plateau: A plateau is a flat-topped elevated area of land, often with steep sides. This term does not accurately describe the practice of layering vegetable wastes and night soil to form a mound.
3. Windrow: As previously explained, a windrow is a row of organic material, such as vegetable wastes and night soil, piled above the ground in alternating layers to facilitate decomposition. This option seems to accurately describe the described practice.

Based on the provided options and their descriptions, "windrow" appears to be the most appropriate term to describe the practice of piling layers of vegetable wastes and night soil alternately to form a mound. However, if "none of these" is the correct answer, it suggests that none of the options accurately describe the described practice. In this case, it implies that there might be another term not listed in the options that accurately describes the method. Without additional context or alternative terms, it's challenging to provide a specific explanation for why "none of these" might be chosen as the answer. In a real-world scenario, if the term used in a particular context does not match any of the provided options, "none of these" could be a valid choice. It's essential to consider the specific terminology and context of the question when selecting the correct answer.