9. Line segment using ruler and compass

 

Step 1: Draw a line $l$. Mark a point $A$ on a line $l$.

 

Step 2: Place the compasses' pointer on the zero mark of the ruler. Open it to place the pencil point up to the $2$ $cm$ mark.

 

Step 3: Please see that the opening of the compass has not changed, place the pointer on $A$ and swing an arc to cut the line $l$ and then mark the point as $B$.