Consider statements about vitamins: 1. Vitamin D is synthesized in the skin upon sunlight exposure. 2. Vitamin B12 is the only vitamin containing a metal ion. 3. Vitamin A is essential for blood clotting. Which are 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:
Gymnosperms have naked seeds on cones, not in an ovary; hence no fruit. Angiosperms have enclosed seeds. R correctly explains A.

Explanation:
Xylem is the vascular tissue responsible for the unidirectional upward transport of water and dissolved minerals from the roots to the aerial parts of the plant. Phloem is the vascular tissue responsible for the translocation of organic nutrients (primarily sucrose) from sources to sinks, which can be bidirectional. Cambium (vascular and cork) is a lateral meristem responsible for secondary growth (increase in girth); primary growth (increase in length) is driven by apical meristems. Thus, statements 1 and 2 are correct.