How can one tell if you are in the reverse position when usi

How can one tell if you are in the reverse position when using a total station?
a- In reverse horizontal angles decrease in a clockwise direction
b- Distance can never be measured in the reverse position
c- The zenith circle is between 180 and 360 degrees
d- Horizontal circle between 180 and 360 degrees define reverse position

Solution

(c) The zenith circle is between 180 and 360 degrees

In reverse position, when the instrument axis is in horizontal plane, it reads 270 degrees on the vertical circle, that means the zenith angle is 270 degrees. Now you can +-90 degree, and get 180 to 360 degrees of circle.