There are seven materials : Pure water , air , copper , aluminium , plastic , steel and glass .Out of these , how many materials are insulators ?

Explanation

To determine how many materials from the given list are insulators, we need to identify which materials do not allow electric current to flow through them. Here’s a step-by-step solution:

### Step 1: List the materials
The materials given are:
1. Pure water
2. Air
3. Copper
4. Aluminium
...