Final answer:
In milling, the L:D ratio typically decreases due to shorter and more rigid tools, whereas in drilling, it increases because drills are designed slender and longer for deep-hole applications. Answer choice 'B) Decreases, increases' correctly reflects the impact of these two different machining processes on the L:D ratio.
Step-by-step explanation:
The puzzle of how different machining processes affect the length-to-diameter ratio (L:D ratio) is intriguing. For milling, the L:D ratio typically decreases because the operation involves cutting a workpiece with a milling tool where the tool length is often shorter in relation to its diameter to provide greater rigidity and accuracy. On the other hand, for drilling, the L:D ratio usually increases since drills are often slender and longer compared to their diameter, particularly for deep-hole drilling operations to reach far into the workpiece. Therefore, the correct response to the student's question would be 'B) Decreases, increases' which aligns with how milling cuts are usually more shallow, hence the lower L:D ratio, while drilling involves deeper penetration yielding a higher L:D ratio.