Final answer:
A biologist would most likely investigate the effect of drier growing conditions on the size of coffee beans, which fits within the field of biology due to its focus on plant-environment interactions.
Step-by-step explanation:
The question a biologist would most likely investigate is: "Do drier growing conditions affect the size of coffee beans?" This inquiry falls within the realm of biology as it concerns the effects of environmental conditions on plant growth, which can be studied by considering variables such as soil moisture, plant physiology, and stress responses in coffee plants.
Biologists study living organisms and their interactions with the environment, which includes understanding how changes in climate or soil conditions can impact plant development. The other questions listed either relate to personal preference, food science, or physical processes of preparing coffee, which are more relevant to psychology, chemistry, and culinary studies, respectively.