Which of the following statements about the brain is correct? MCQ with Answer and Explanation

Explanation:
Telomerase is a ribonucleoprotein enzyme that adds repetitive nucleotide sequences to the ends of chromosomes (telomeres), preventing them from shortening during DNA replication. It is highly active in germ cells, stem cells, and most cancer cells, granting them replicative immortality. In most normal somatic cells, telomerase is inactive, leading to gradual telomere shortening and cellular aging.

Explanation:
Motilin is a peptide hormone secreted by the Mo cells (or M cells) in the crypts of the duodenum and jejunum. Its secretion occurs in cycles during the fasting (interdigestive) state. Its primary function is to stimulate gastric motility and emptying, and to initiate and regulate the Migrating Motor Complex (MMC). The MMC is a pattern of electromechanical activity observed in the gastrointestinal tract during fasting, characterized by waves of contraction that sweep undigested material, bacteria, and sloughed cells from the stomach and small intestine towards the colon, acting as a 'housekeeper'.

Explanation:
Earthworms have hemoglobin dissolved in their blood plasma (not in cells) for oxygen transport. Hemocyanin is in mollusks and arthropods, hemerythrin in some marine worms.