8) What is the name of the staff 3m long and the band fitted is graduated in mm used for precise levelling?

9) What is the smallest graduated division in levelling staff?

10) What is the message to indicate the movement of leftarm over 90 Degree?

11) What is the process if the difference of level between two points is determined by setting the levelling instrument midway between the point?

12) Which type of the collimation error is eliminated?