On a distance-time graph, if an object is stationary, the total distance travelled must be zero.

This statement is not necessarily true. On a distance-time graph, if an object is stationary, it means that the object is not changing its position over time. However, this does not necessarily mean that the total distance travelled by the object is zero. The object could have travelled a certain distance before becoming stationary. The graph would show a horizontal line at the point representing the distance the object travelled before it stopped moving. This horizontal line could be at any point on the distance axis, not just at zero, indicating that the object has travelled some distance before becoming stationary.