Which of the following could be an indicator that a tenant is growing illegal marijuana?

Excessive water and electricity bills can be strong indicators that a tenant may be growing illegal marijuana. This activity typically requires substantial resources for things like watering plants and maintaining optimal lighting conditions. Indoor cultivation often results in notably higher utility bills, as the growing process demands significant water and electricity for irrigation systems, grow lights, heaters, and ventilation systems. Therefore, if a landlord notices a consistent spike in these utility costs that cannot be accounted for by normal usage patterns, it may warrant further investigation regarding the potential for illegal activities on the property.

While high foot traffic at odd hours, strong odors of chemicals, and unauthorized pets may also raise suspicions, they are not as directly correlated with the specific signs of illegal grow operations as the sharp increase in utility bills. Thus, excessive water and electricity bills stand out as a key indicator in this situation.