ANS:B - is minimum if the staff is held truly normal to the line of sight.

If staff is not vertical, the reading will be too great. If staff is normal to the line of sight the value will be minimum or accurate. It will not be maximum. The intercept of staff increases when it is tilted away from norman and decreases or gets minimum when moved towards normal. Staff intercept is the difference in reading between top and bottom cross hairs. If the staff is tilted forward or backward from normal, the staff intercept will increase. It is minimum when staff is truly vertical. Reading will increase in both cases, if tilted away or towards. Because it's minimum when staff held normal. So you can't go below the minimum. So answer D is also correct but B is more logical. Staff intercept: is the difference between the reading measured at top cross hair and bottom cross hair of telescope.