help me please :/ if you don't know what the answer please don't answer or i will report you answer

What percent of the circle below is shaded?

Atriangle with all sides of equal length is a/an triangle. a. right b. scalene c. equilateral d. isosceles

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.