Option C is correct.
We know an isoceles triangle has two sides of equal length. Let's take the length of the sides as 6 cm, 6 cm and 4 cm.
We can only divide from the middle. If we try also to divide it from other angles we cannot.

Symmetry refers to the balanced arrangement of shapes or objects when they are divided into two equal parts. In geometry, lines of symmetry are lines that divide a shape into two identical halves. An isosceles triangle is a type of triangle that has two sides of equal length.

Lines of Symmetry in an Isosceles Triangle:
An isosceles triangle has only one line of symmetry. This line is called the axis of symmetry or the line of symmetry. It is the line that divides the triangle into two congruent halves.

Explanation:
1. Definition of an isosceles triangle:
- An isosceles triangle is a triangle that has at least two sides of equal length.
- In other words, it is a triangle with two congruent sides.
- The third side of an isosceles triangle is called the base.

2. Understanding lines of symmetry:
- A line of symmetry is a line that divides a shape into two identical halves.
- When a shape has multiple lines of symmetry, it means it can be folded along those lines to match both halves perfectly.

3. Identifying lines of symmetry in an isosceles triangle:
- In an isosceles triangle, the line of symmetry is the line that passes through the vertex angle (opposite the base) and the midpoint of the base.
- This line divides the triangle into two congruent halves.

4. Visual representation:
- Imagine an isosceles triangle with two equal sides and a base.
- Draw a line from the vertex angle (opposite the base) to the midpoint of the base.
- This line divides the triangle into two congruent halves, with each half being a mirror image of the other.

5. Conclusion:
- An isosceles triangle has only one line of symmetry, which is the line passing through the vertex angle and the midpoint of the base.
- Therefore, the correct answer is option 'C' - 1.