Final answer:
Diagonal pliers are the best option for cutting heavy-duty wire because they are specifically designed for that purpose and have the necessary sharp edges for efficient cutting.
Step-by-step explanation:
The appropriate type of pliers for cutting heavy-duty wire is diagonal pliers. Diagonal pliers are designed specifically for cutting wire and have sharp edges that make it easy to snip through thick wire. Needle-nose pliers are for precision work, slip-joint pliers are for gripping and turning, and locking pliers are for securing objects tightly. But diagonal pliers have the right build to cut heavy wire efficiently.