Final answer:
The key to preparing biscuit dough successfully is to handle the dough gently to maintain the coldness of the butter, which is essential for achieving a flaky texture.
Step-by-step explanation:
The key to success in preparing biscuit dough is d. Handling the dough gently. This is because biscuits rely on cold butter creating steam when baked, which results in a flaky texture. Overmixing or handling the dough too much warms the butter and can lead to tough biscuits. It is also important to use the right balance of ingredients and to avoid using stale ingredients to ensure the best flavor and texture.