Consider statements about human nutrition: 1. A balanced diet contains all essential nutrients. 2. Malnutrition can be caused by overeating. 3. Water is not a nutrient. Which are correct? MCQ with Answer and Explanation

Explanation:
While the Blood-Brain Barrier (BBB) protects most of the brain, there are specific areas where the BBB is absent or highly permeable. These are the circumventricular organs (CVOs), which are located around the third and fourth ventricles. Because they lack a typical BBB, they can directly sample the chemical composition of the blood and cerebrospinal fluid. This is essential for their functions, which include neuroendocrine regulation (e.g., the area postrema for vomiting, the organum vasculosum of the lamina terminalis for osmoregulation, and the median eminence for hormone release).

Explanation:
Rhizobium species form symbiotic root nodules in legumes and fix atmospheric nitrogen into ammonia. Azotobacter is free-living, Nitrosomonas nitrifies, Lactobacillus ferments.

Explanation:
Sclerenchyma cells have thick, lignified secondary walls and are often dead at maturity, providing rigid structural support. Fibers and sclereids are examples. Parenchyma is living and thin-walled, collenchyma living with uneven thickening, aerenchyma has air spaces.