From the picture you are showing me, the last option is the correct one, it means dipeptide. Remember that a dipeptide is a peptide composed of two amino-acid residues. And that is shown in the image. Hope this helps
When calcium chloride pellets are crushed with feet it increases the surface area of the calcium chloride. As the surface area increase the number of collision between the reactant molecules increases. Here the reactant molecules are calcium chloride ions and water molecules. In the process of dissolution the calcium chloride ions get hydrated by the dipoles of the water molecules. As the frequency of collision increases it lowers the activation energy or threshold barriers to start a reaction.
