The OH on the lower right of lysine and the H on the lower left of valine combine to form a molecule of water (H2O) and detach in a process known as a dehydration reaction when the two amino acids bond. The C on the right side of lysine then single bonds with the N on the left side of valine. This bond is termed a peptide bond. All the other bonds remain unchanged.
Water is a very polar molecule.
This means there is a (slight) difference in charge between the ends of the water molecule. Water is made up of an Oxygen and two Hydrogens (H₂O). The Oxygen is a much larger atom, with 8 protons in its nucleus, whereas Hydrogen has only 1 proton.
As protons are positively charged, the oxygen has a greater positive charged, so the electrons which are negatively charged are more attracted to the Oxygen, and the bond shifts slightly towards the oxygen. As the electrons have shifted position, the negative charge has shifted position, to there is a slight negative charge nearer the Oxygen, δ⁻ (delta minus), and a slight positive charge, δ⁺ (delta plus), at the Hydrogen.
This allows strong inter molecular forces to occur, as the slightly positive Hydrogens are attracted to the slightly negative Oxygens. This force of attraction between water molecules causes them to want to 'stick together', causing a high surface tension.
So the answer is B)
A. Response is the system's reaction to the stimulus.
It doesn't have to be irritability - not every stimulus is unpleasant. And also, it's not adaptability, because you cannot always adapt to a stimulus, for example, to pain.
