If altitude bubble is provided both on index frame as well as on telescope of a theodolite, then the instrument is levelled with reference to
i) altitude bubble on index frame
ii) altitude bubble on index frame if it is to be used as a level
iii) altitude bubble on telescope
iv) altitude bubble on telescope if it is to be used as a level
The correct answer is

A. only (i)

B. both (i) and (iv)

C. only (iii)

D. both (ii) and (iii)

Answer: Option B