Poor maintenance of the HVAC system contributes to mold growth.

Poor maintenance of the HVAC system indeed contributes to mold growth, making this statement true. HVAC systems are crucial for regulating indoor humidity and temperature. If these systems are not properly maintained, they can create an environment conducive to mold development.

For instance, a neglected HVAC system can accumulate dust and debris, which provide organic material for mold spores. Additionally, if the system's filters are not changed regularly, moisture can build up due to inadequate airflow, further enabling mold proliferation. High humidity levels, often a result of malfunctioning or poorly maintained systems, are a significant factor in mold growth.

While the other choices indicate specific conditions that might influence mold growth, they do not recognize the broader impact of overall HVAC maintenance. Regardless of the type of HVAC system or the replacement frequency of filters, if the system is not serviced and maintained effectively, it can lead to moisture problems, which are pivotal in the development of mold. Therefore, emphasizing regular maintenance of HVAC systems is essential to prevent mold issues in indoor environments.