Sure, here are four English letters that have no line of symmetry:

1. Letter "S"
2. Letter "J"
3. Letter "R"
4. Letter "K"

Certainly! Here are five English letters that have a horizontal line of symmetry:

1. Letter "A"
2. Letter "H"
3. Letter "M"
4. Letter "O"
5. Letter "U"

The letter "Z" of the English alphabet has 2 lines of symmetry.

1. The first line of symmetry is vertical, passing through the center of the letter, dividing it into two mirror-image halves.
2. The second line of symmetry is diagonal, passing from the upper-left corner to the lower-right corner, dividing the letter into two congruent triangles.

So, the letter "Z" has 2 lines of symmetry.

The letter "O" of the English alphabet has infinite lines of symmetry.

Any line passing through the center of the letter "O" will divide it into two mirror-image halves that are congruent. Since there are infinite lines that can pass through the center of the letter "O", there are infinite lines of symmetry for the letter "O".

The number of lines of symmetry of an nn-sided regular polygon depends on the value of nn.

For a regular polygon:

1. If nn is odd, there are nn lines of symmetry. Each line passes through a vertex and bisects the opposite side, creating nn lines of symmetry.
2. If nn is even, there are n/2n/2 lines of symmetry. Each line passes through a vertex and bisects the opposite side, creating n/2n/2 lines of symmetry. Additionally, there is a line of symmetry passing through the midpoints of two opposite sides.

In summary:

• If nn is odd, there are nn lines of symmetry.
• If nn is even, there are n/2n/2 lines of symmetry.

So, the number of lines of symmetry of an nn-sided regular polygon is nn if nn is odd, and n/2n/2 if nn is even.