A line of symmetry divides a shape into two matching parts, which will overlap each other exactly when folded along the line of symmetry.

Look at this **regular hexagon**.

When we reflect or fold it in the **line a**, we get:

This is a MATCH!

When we reflect it in the **line b**, we get:

This is **not **a MATCH!

When we reflect it in the **line c**, we get:

This is a **MATCH!**

When we reflect it in the **line d**, we get:

This is a **MATCH!**

So **lines a, c and d **are lines of symmetry.

Of course, a regular hexagon has a total of 6 lines of symmetry, but not all of them were shown.