Who is a septic tank manufacturer?

The correct answer identifies a corporation that specifically engages in the manufacturing of septic tanks and associated units. This option is clear in its definition because a septic tank manufacturer is someone involved in the production of these tanks, which includes creating them from various materials and ensuring they meet regulatory standards. The role is defined by the creation and design of the product rather than installation, maintenance, or oversight of regulations.

In contrast, the other options focus on related but different responsibilities. Installing septic tanks involves the physical setup of the units on a property, which is a distinct role from manufacturing. Maintenance covers the ongoing care and servicing of septic systems to ensure they operate effectively, which also does not pertain to the actual production of tanks. Finally, overseeing septic tank regulations pertains to compliance and regulatory activities rather than the physical creation of septic tanks. Each of these roles plays an important part in the septic system lifecycle but does not fulfill the specific function of manufacturing.