Which of the following methods can be employed to aid in drilling through hardened metal?

Using a carbide bit is the most effective method for drilling through hardened metal due to its superior hardness and abrasion resistance. Carbide is a composite material that can withstand the heat generated during the drilling process, making it particularly suitable for challenging materials that would quickly dull lesser bits. Its properties allow for more efficient drilling without losing the cutting edge, which is critical when working with hardened metals.

In contrast to other options, high-speed steel bits, while useful for a variety of drilling applications, tend to struggle with hardened materials as they are less durable and can quickly lose their sharpness, leading to inefficient drilling or potential damage to the bit. Standard bits that haven't undergone any special treatments are also not designed for the toughness of hardened materials and will similarly degrade rapidly. Woodworking bits, on the other hand, are specifically designed for softwood and hardwood and are not suitable for metal at all; their design lacks the structural integrity and cutting characteristics necessary for effective metal drilling.