Five letters, T, E, A, M and S are drawn on a square grid.

1. Determine which letters have at least one line of symmetry

By inspecting the block letters:

• T: Has a vertical line of symmetry.
• E: Has a horizontal line of symmetry.
• A: Has a vertical line of symmetry.
• M: Has a vertical line of symmetry.
• S: Has no line of symmetry (only rotational symmetry).

2. Count the number of letters with a line of symmetry

The letters T, E, A, and M have lines of symmetry.
Total number of letters = $4$.

1. Identify letters with parallel lines

Looking at the letters:

• T: No parallel lines.
• E: Has three horizontal strokes which are parallel to each other.
• A: No parallel lines.
• M: Has two vertical strokes which are parallel to each other.
• S: Curved, no straight parallel lines.

2. Identify letters with perpendicular lines

Looking at the letters:

• T: Has a horizontal top stroke and a vertical stem, which are perpendicular.
• E: Has horizontal strokes and a vertical stroke, which are perpendicular.
• A: No perpendicular lines.
• M: No perpendicular lines (vertical and slanted strokes do not meet at $90^\circ$).
• S: Curved, no perpendicular lines.

3. Find letters with both parallel and perpendicular lines

From the analysis:

• T has perpendicular lines but no parallel lines.
• E has both parallel lines (the three horizontal strokes) and perpendicular lines (horizontal strokes meeting the vertical stroke).
• M has parallel lines but no perpendicular lines.
  Therefore, only E has both.