A vertical line is a straight line that points to the center of the earth.
HORIZONTAL LINES.
The straight line o p points to the horizon.
It is called a horizontal line.
Read all the horizontal lines.
A horizontal line is a straight line that points to the horizon.
OBLIQUE LINES.
The line s t points neither to the center of the earth nor to the horizon.
It is called an oblique line.
Read all the oblique lines.