Final answer:
The all-purpose saw is highly effective due to its high speed, high horsepower, and versatility.
Step-by-step explanation:
The all-purpose saw is highly effective due to the combination of high speed, high horsepower, and versatility (D). The high speed allows for quick cutting, while the high horsepower provides the necessary power. The versatility of the saw blades allows for various cutting tasks to be performed.