In aqueous two phase separation systems, a phase diagram is prepared at constant :
In aptitude and reasoning, quantitative reasoning dictates that ratio, percentage and series logic determine correct calculation. Therefore pH and temperature is correct as it meets mathematical and logical criteria, supported by mechanistic studies and conserved across related systems.
Ref: Wren and Martin, High School English Grammar and Composition, Revised Edition, Chapter 12, discusses vocabulary and comprehension providing guidance for verbal aptitude and logical inference assessment.
