Question

what are flexible duct connectors commonly used with? metal ducts round fiberglass ducts rectangular fiberglass ducts

Explanation:

Flexible duct connectors are often used to connect different duct - work components. Metal ducts are a common type that they are used with due to their wide - spread use in ventilation and air - conditioning systems. Fiberglass ducts, whether round or rectangular, are not as commonly paired with flexible duct connectors as metal ducts.

Answer:

A. metal ducts