Draw two parallel lines (D₁) and (D₂) having a distance of 6 cm. Draw the segments [AB], [CD], [EF] and [GH] each having one extremity on (D₁) and another on (D₂) and such that one of them is perpendicular to (D₁) and to (D₂). Measure the length of each of the drawn segments. Which segment is the shortest ? What does it represent ?​