c) The physiological process being investigated is respiration.

c) The physiological process being investigated is respiration.

d) A word equation for the physiological process (assuming anaerobic respiration in yeast, a common experiment in a boiling tube) is:

$$\text{Glucose} \rightarrow \text{Ethanol} + \text{Carbon dioxide} + \text{Energy}$$

e) A warm water bath was used to provide an optimum temperature for the enzymes involved in respiration, which increases the rate of reaction. It also helps to maintain a constant temperature throughout the experiment.

f)

i) You should draw a yeast cell. Label its key structures, such as the cell wall, cytoplasm, and nucleus (or vacuole/bud if present).

ii) The magnification of your drawing would typically be much higher than the microscope's magnification to show detail. A common magnification for such a drawing is x1000 or x2000.

iii) The identity of substance D cannot be determined from the provided image, as there is no context or diagram referring to "substance D".