The Robots want to find out about different types of life on our planet. On their planet there is no life. They have discovered that we have different types of life in addition to ourselves. In particular they are fascinated by the idea of plant life. But they don't know what makes a plant a plant.
Their first question is: "Are all plants green?"
Use wipe-boards,and paper, magnifying glasses, small plastic zip-lock bags or plastic containers to ‘collect the evidence. If possible, use technology such as an iPad or tablet to assist in recording the evidence and send it to email@example.com