The best title for Paulo's presentation would be "How Plants Differ". This is because it is the most general title that encompasses all of the information in his notes. The other options are either too specific or not specific enough.
How Plants Differ is a good title because it covers all of the following points:
Plants can be divided into three groups: non-vascular, vascular, and seed-bearing.
Plants can be small or large, depending on the species.
Plants have specialized tissues, but they also use other mechanisms, such as active transport.
Some plants have true stems and leaves, while others do not.
The other options are not as good because they do not cover all of these points. For example, "Can Be Almost Any Size" is too specific because it only covers one of the points (that plants can be small or large). "How Plants Work" is not specific enough because it could cover a wide range of topics, not just the characteristics of plants.
Therefore, the best title for Paulo's presentation is "How Plants Differ".