Cant be the yellow circle because Colon woupdvd known right away. Likewise it cant be the square or Shilpa wouldve known. You can eliminate from there using deductive reasoning
Okay. If the shape was square, or the color was yellow, one of the people would know in one round. So, we can eliminate the yellow circle or blue square. Then, if the color was blue, after the first round, where the shape guy didn't say anything, the color guy would know it is blue triangle, so we know it isn't blue triangle. Likewise, if the shape was circle, after the first round, if the color guy did not say yellow circle, the shape guy would know it is green circle, so we know that is not the case. Therefore, the only possible answer is green triangle.
answer is green triangle
each time you can eliminate 2 objects
first time yellow circle and blue square
second time blue triangle green circle
leaving green triangle