单项选择题
Previously, the sack-like rabbit appendix was thought to serve primarily as a reservoir for the bacteria involved in hindgut fermentation, a explanation that failed to account for the absence of an appendix in other animals with similar digestive systems or for its presence in humans. Microscopic research revealed that the appendix contains a significant amount of lymphoid tissue, similar aggregates of which tissue occur in other areas of the gastrointestinal tract. These are involved, possibly, in the body’’s ability to recognize foreign antigens in ingested material, but the evidence is inconclusive, to the extent that scientists have long discounted the human appendix as a "vestigial" organ. However, a growing body of evidence suggests that the appendix, far from being a "vestigial organ", hag a significant function as a part of the body’s immune system. The appendix achieves its greatest development shortly after birth, when immune response is first developing, then regresses with age, when the immune response mediated by the appendix may relate to such inflammatory conditions as ulcerative colitis, which in adults necessitates the organ’s surgical removal.
The passage provides information in support of which of the following assertions（） A．Lymphoid tissue somehow involved in the body’’s ability to recognize foreignantigens in ingested material is a primary cause of ulcerative colitis.
B．The appendix is an anomaly among mammals, existing in rabbits and humans largely as an evolutionary fluke.
C．Microscopic research is insufficient to give even the vaguest suggestion of what the human appendix’’s function may be.
D．The digestive process in human beings is less dependent on the hindgut fermentation process than is the digestive process in rabbits.
E．Lymphoid tissue that recognize foreign antigens is absent in the digestive systems of animals that lack appendixes.