In levelling operation
(A) When the instrument is being shifted, the staff must not be moved
(B) When the staff is being carried forward, the instrument must remain stationary
(C) Both (a) and (b)
(D) Neither (a) nor (b)
(A) When the instrument is being shifted, the staff must not be moved
(B) When the staff is being carried forward, the instrument must remain stationary
(C) Both (a) and (b)
(D) Neither (a) nor (b)