Write an expression that equals 40. include am exponent

Match the term on the left with its image or description on the right. match term definition diameter a) circle a and a line segment connecting points b and c which are on the circle. circumference b) circle a and a line segment connecting points b and c which are on the circle. radius c) a piece of the circumference of a circle secant d) two circles that share the same center. concentric circles e) the distance around a circle arc f) a segment between two points on a circle that passes through its center

Ineed me i stuck and i don’t want to get it wrong

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.