I am having some trouble with figures and graphs in comparison questions. To what extent can we believe in the figure? For example if there is a line drawn in a circle, and it is above the diameter of the circle (diameter not drawn in graph), can we assume that line is drawn above the diameter? Or if there is a shape that looks regular, but the questions doesnt state that its regular, nor are there any angles or sides given to indicate its regular, do i have to consider it irregular?

I am having trouble deciding what information I can use for solving these questions.