I think the correct answer would be the third option. The criteria that could help Linda in classifying whether the gases are greenhouse gases would be gas molecules having at least one oxygen atom. Most of the greenhouse gases has an oxygen atom in their structures especially those that naturally occurs. These gases are CO2, H2O vapor and nitrous oxide.
-- There is no need to develop the pictures. They are available immediately in a digital camera.
-- There is no change in the teacher from one picture to the next.
-- The distance the watermelon falls from the teacher in each new picture is more in each picture than in the picture before it. (C)
