ANS:B - affected by pressure.

The statement "Boiling point diagram is affected by pressure." is correct. The boiling point diagram, also known as the phase diagram or boiling point curve, illustrates the relationship between temperature and pressure at which a substance transitions between its liquid and vapor phases. This diagram is indeed affected by pressure because changes in pressure alter the boiling point of a substance. At higher pressures, the boiling point of a substance increases, while at lower pressures, the boiling point decreases. This is due to the fact that pressure affects the equilibrium between the liquid and vapor phases. Consequently, changes in pressure lead to shifts in the boiling point curve on the phase diagram. So, the correct statement is: "Boiling point diagram is affected by pressure."