The answer to this question would be simple squamous epithelium.
When you need to supply oxygen or nutrient, the thinner cell layer the faster it can move. In this case, simple squamous epithelium is better since it provides protection but can let the nutrient transported quickly.
When using a dichotomous key you look for the QUALITATIVE and QUANTITATIVE attributes of your specimen. Qualitative meaning the simple appearance such as color or the size. Quantitative meaning height, wings or no wings, tail or no tail, etc.
Hope this helps
The antacid tablet because it stays the same through out the whole experiment while the water tempratures
