Which of the following is a sign of potential septic system failure?

Each of the signs listed can indicate potential issues with a septic system, making the choice of all of the above appropriate.

Healthy green grass in the drain field area can seem like a positive sign at first glance. However, it may indicate that the septic system is failing and that effluent is surfacing in the drain field, allowing excess nutrients to promote lush growth in that area. This can suggest that the system is overloaded or malfunctioning.

Slow draining sinks and toilets are a clear sign of plumbing issues, which often relate to septic system problems. These slow drains can result from blockages in the pipes or a full septic tank that is unable to properly process waste, thereby leading to backups and stating that the system requires attention.

Odd odors near the septic tank indicate that gases, liquids, or other contents may not be contained within the system as they should be, pointing toward a failure of the containment and treatment aspects of the septic system.

Since each of these signs reflects potential septic system failure, the choice indicating that all of these signs together are relevant is indeed correct. Recognizing these warning signs is crucial for prompt maintenance and preventing more severe problems down the line.