Note for the Teacher
The preparation for the lab is reasonably simple the four solutions are as follows:
A is pure water;
B is water with blue food coloring (make this reasonably dark see below);
C is very dilute HCl;
D is Bromo Thymol Blue solution.
The "art" of the preparation for the lab is to make sure that the water with blue color and the indicator solution are as close to the same color as possible. This means increasing the Ph of the indicator by adding dilute NaOH until a suitable color match is achieved. The problem is that while the indicator does indeed become "bluer"; adding too much NaOH will make the indicator so basic that it does not respond to the breath test. You will have to play a bit before hand to get the indicator and blue dye solutions right.