Final answer:
The 'Principal fiber group' in the context of fibrous connective tissue corresponds to the Connective tissue in the skin, particularly the dermis, due to its rich collagen content and ability to handle stress from various directions.
Step-by-step explanation:
The 'Principal fiber group' referred to in the question is associated with fibrous connective tissue, which is a type of tissue that is rich in collagen fibers and provides support and strength to various parts of the body. Given the choices, Connective tissue in the skin, specifically the dermis of the skin, contains irregularly arranged fibrous connective tissues that handle stress from multiple directions due to the large amounts of collagen fibers present. These collagen fibers are flexible yet have great tensile strength, which provides resilience and strength to the skin.