Final answer:
Fused ring system compounds contain interconnected rings sharing common carbon atoms; in steroid hormones, this typically involves three six-membered rings and one five-membered ring with a trans-fused configuration.
Step-by-step explanation:
Compounds with a fused ring system are those with two or more rings sharing common carbon atoms. When such a system comprises three 6-membered rings and one 5-membered ring, it often refers to the core structure of steroid hormones. This structure includes rings designated A, B, and C, which are six-membered, and a ring designated D, which is five-membered. These rings are fused together, sharing adjacent carbon atoms known as the bridgehead carbons. Each bridgehead carbon has bonds to carbons in both of the connected rings. Steroid hormones typically have what is called a trans-fused configuration for rings B, C, and D, meaning that the substituents at the ring fusion are equatorial, minimizing steric strain and providing a stable structure.