The letter 'S' when rotated by an angle of ${180}^{\circ }$ will look exactly the same as before. 
Thus, it has rotational symmetry of order 2. 
The letter S does not exhibit line symmetry.

A shape has line symmetry when one half of it is the mirror image of the other half. A mirror line helps us visualise line symmetry.

If a mirror is kept vertically passing through the centre of letters A, H, I, M and W, the exact same reflection appears.
If a mirror is kept horizontally passing through the centre of letters B, C, D, E and H, the exact same reflection appears.

Similarly, letters O and X have reflection symmetry about both horizontal and vertical mirrors.

Order of rotational symmetry of the letter X about the point of intersection of the lines is 2.

The statement is true. Diameter is the line of symmetry of a circle.

No two sides in a scalene triangle are equal. So, it's not a symmetrical figure. Any object that occupies the same position after a rotation of ${360}^{\circ }$ has a rotational symmetry of order 1.

Order of rotational symmetry of an equilateral triangle about the centroid of the triangle is 3.

If we rotate a figure about a fixed point by a fixed angle (other than ${360}^{\circ }$) and obtain the same figure, then it is said to have rotational symmetry of order more than 1.
The letter C does not have rotational symmetry of order more than 1 as it can be rotated only by an angle of ${360}^{\circ }$ to come back to its original position.

Letters H and O have both line symmetry and rotational symmetry. Z has only rotational symmetry.

A regular polygon has as many lines of symmetry as the number of sides it has.

So, an 'n'-sided regular polygon has 'n' lines of symmetry.

False. As $\frac{360}{17}$ is not a natural number, a figure can not have an angle of rotation as ${17}^{\circ }$.