A hacksaw blade is specified by its

Answer: Option A

A hacksaw blade is primarily identified and ordered by its length.
Think of it like buying a piece of wood – you need to know how long it is!

Here's why the other options are less important for initial specification:

Option B: Material: While the material (like high-speed steel) is important for performance, it's usually a secondary specification.
Option C: Width: The width is generally standardized, and not the first thing you'd use to specify a blade.
Option D: Number of teeth: The number of teeth (or TPI - Teeth Per Inch) is also important for the type of material you're cutting, but again, length is the primary identifier.

So, when you go to buy a hacksaw blade, you'd typically ask for a "12-inch blade" (length) first, then specify the type of material and TPI depending on your needs.