A student is investigating the effect of different factors on the growth of a certain type of bean plant over 30 days. Which factor would not function as a variable in this investigation?

A variable function is something that changes throughout an experiment.

Here given is - A student is investigating the effect of different factors on the growth of a certain type of bean plant over 30 days.

Though options are not given but still, it is clear that the type of the plant here cannot be variable.

This is because, various factors will be applied on the same plant to check its growth.

Hence, the bean plant type will remain constant.