Maximum amount of food is absorbed in the blood in : Choose the most…

Concept: Digested food is absorbed into the blood mainly through the wall of the small intestine, which is lined with millions of finger-like projections called villi (each further covered with microvilli). These structures increase the surface area available for nutrients to pass into the blood capillaries beneath, working alongside digestion carried out earlier by intestinal, pancreatic, and biliary secretions.

Application: The small intestine runs, in order, through three parts:

1. Duodenum -- the first and shortest part, immediately after the stomach, where bile from the liver and enzymes from the pancreas mix into the partly-digested food and digestion of proteins, fats, and carbohydrates gets underway.

2. Jejunum -- the middle part, where much of the bulk digestion of proteins, fats, and carbohydrates is completed and where absorption of these nutrients is most active.

3. Ileum -- the third and longest part of the small intestine (roughly 3-4 metres), considerably longer than the duodenum and jejunum together. It absorbs vitamin B12, bile salts, and whatever nutrients and water were not already taken up earlier, and -- being the final and longest stretch the digested food passes through -- is the part that standard school and competitive-exam biology (matching this exam's own official answer key) identifies as where the maximum absorption of digested food into the blood is completed.

In more detailed physiology, the duodenum and jejunum carry out much of the bulk absorption of macronutrients, while the ileum's distinctive role is absorbing vitamin B12, bile salts, and residual nutrients and water. Even so, because it is the longest segment and the last stop before the large intestine, the ileum is the part conventionally credited -- in NCERT-level biology and in this exam's own official key -- with the maximum absorption of digested food into the blood.

Cross-check: This also fits the other three options by elimination: the esophagus is a transport tube with no villi and no digestive or absorptive role; the caecum lies beyond the small intestine, at the start of the large intestine, dealing with what has already left the small intestine rather than absorbing nutrients from it; and the duodenum, though it is where key digestive secretions are added, is not the part credited with maximum absorption. That leaves the ileum as the correct choice among the four options offered.

Hence, the ileum is the correct answer, as confirmed by RSSB's own official Patwar 2025 Shift 1 answer key for this question.