The third step in the process is:
Correct sequence is :
Step 1 . Draw a line PQ and take a point A anywhere outside the line.
Step 2. Place the pointed end of the compass on A and with an arbitrary radius, mark two points D and E on line PQ with the same radius.
Step 3. From points D and E, mark two intersecting arcs on either side of PQ and name them R and S.
Step 4. Join R−S passing through A.
So the third step is 3.