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In this problem, I realised that to get the smallest result, each question asked would have to halve the number of shapes left until you have the final shape. Therefore, the minimum amount of questions you could ask and certainly get a right answer is three: 8 divided by 2 = 4; 4 divided by 2 = 2 and 2 divided by 2 = 1, which makes a total of 3 questions. You could use any question that halved the number of shapes each time but I have only used these ones here as an example. (See attachment). Therefore, the minimum number of questions before a person could certainly guess the shape is three.