In the picture of this experiment, we can see three different layers from top to bottom a yellow one, a white one, and a brown one. We can see also that they differ one from another, not only in their color but in their content. This is due to the yellow layer being in fact the part of the cell membrane which is closer to the extracellular media, while the brown layer is the part of the cell membrane which is closer to the cytoplasm of the cell.
The reason of this is because the majority of the cell membrane proteins are closer to the cytoplasm rather than to the extracellular media.
Having this clear, we can say that the correct answer to the question is the first one: A. Daniel Branton's freeze fracturing image revealed that the small bumps in the membrane are the proteins of the cell membrane.