Overwatering or underwatering is the main cause of injury or death in many indoor plants. Improper watering leads to root rot or dehydration, both of which severely affect plant health.
Ventilation (A) affects air circulation but is rarely the direct cause of death.
Humidity (C) affects moisture levels but is less critical than watering.
Temperature (D) influences plant growth but is not the main cause of injury or death.
Proper watering practices are essential to maintain healthy indoor plants.