Yeast Beasts in Actions

What is the problem in this investigation? Which will yield the most reaction when mixed with yeast; acid (soda), base (antacid), or neutral (milk). What I thought is that the acid would be more reactive with yeast, with prior knowledge that acids in past labs have been highly reactive. Results?

We started with our acid and put the yeast in. In the first 30 seconds it went up and down and right after that it started going up. It didn't really stop after that, in fact when we stopped pressing down on the stopper, it popped up. That's a sign that it didn't stop aside from the graph.

After that run, we did the neutral liquid. This was by far, the least reactive with yeast. We put the yeast in and the liquid just sat there and didn't even fizz like the soda did. As you can see from
the graph, it gradually went up but barely.

Last but not least, the base reaction. This really surprised me, it turned out to be the most reactive of all three, therefore my hypothesis was incorrect. I mean just look at the graph, it just shot right up, no hesitation. It fizzed higher than any other liquid.

I concluded that because the base (antacid) is used for stomach relief, it deals with acids and can be just as reactive as an acid.