What is the primary function of a transit in surveying?

Answer: B — To measure vertical angles

The primary function of a transit in surveying is to measure horizontal and vertical angles accurately. While the option indicates the measurement of vertical angles, it's essential to note that transits are primarily known for their ability to measure both horizontal and vertical angles effectively. This ability is crucial in various surveying tasks, such as laying out construction projects and establishing sightlines. When using a transit, operators can align the instrument with specific points on the ground to determine precise angles, which are key in calculations for distances and elevations. This functionality ensures accurate and reliable data collection in surveying work, thereby aiding in the design and construction phases of projects. In addition to measuring angles, transits can also assist in determining elevation indirectly by using the angles measured in concert with distance measurements, proving their versatility in surveying applications.