Which item must be shown on a surveyor's drawing as a basis of direction?

The correct response highlights the necessity of including a basis of direction, which is crucial for establishing the orientation of the survey. In surveying, a basis of direction indicates the frame of reference for determining angles, allowing other measurements and features on the drawing to be related accurately to cardinal directions. This helps in understanding how the plot is situated in relation to the surrounding area and other properties.

In contrast, while a surveyor's signature and date are important for authentication and record-keeping, they do not serve the same purpose of providing direction. A legend is also valuable as it explains the symbols used in the drawing, but it does not communicate spatial orientation. The north arrow is indeed a common element in survey drawings to indicate direction, but it does not inherently represent the framework of reference as clearly as a basis of direction does. Therefore, the inclusion of a basis of direction is essential for clarity and accuracy in surveying documentation.