A student wants to verify the upper fixed point and the lower fixed point on a Celsius scale thermometer. She is given four beakers P, Q, R and S. Beaker P has a mixture of ice and salt. Beaker Q has a mixture of ice and water. Beaker R has boiling salt solution. Beaker S has boiling water. Which two beakers should she choose to check the fixed points?
- AP and R
- BP and S
- CQ and R
- DQ and S