Final answer:
The ST connector is primarily meant for use with both multimode fiber and single-mode fiber optical cable systems, due to its versatile and reliable physical design.
Step-by-step explanation:
The ST connector, or Straight Tip Connector, is commonly used in fiber optic cable systems for joining fiber optic cables. When you are looking at the types of cable systems this connector might be used with, answer A) Multimode Fiber (MMF) connections and B) Single-Mode Fiber (SMF) connections are the correct options. The ST connector is recognized for its cylindrical design, featuring a twist-on/twist-off bayonet mount and a long cylindrical ferrule to hold the fiber. Primarily, it was used with multimode fibers, but it can also be used with single-mode fibers, hence its versatility and popularity in various fiber optic network applications including local area networks, telecommunications, and data processing networks.