Three factors
Every conductor has a resistance, and they are not all the same. Three things about a piece of conductor decide what its resistance is.
Its cross-sectional area
How thick the piece of conductor is — the area of the face you would see if you cut straight across it.
Its length
How long the piece of conductor is, from the point the current enters to the point it leaves.
The material it is made of
Which substance the conductor is — copper, iron, nichrome — quite apart from its shape.
How to find out what each one does
Three factors means three comparisons, and each one has to change a single factor while holding the other two still. That is exactly how the activity on the next page is laid out, and it is worth reading its list of seven wires with this in mind.
Two of the three are shape, one is substance
Area and length are things you could change with a pair of cutters. The material is not — and it turns out to need a property of its own, which is the last page of this skill.