Consider statements about human immunity: 1. Innate immunity is present from birth. 2. Vaccination provides artificial active immunity. 3. Antibodies are produced by T-lymphocytes. Which are correct? MCQ with Answer and Explanation

Explanation:
The double helix structure of DNA was proposed by James Watson and Francis Crick in 1953, based on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins. They proposed that DNA consists of two antiparallel polynucleotide chains coiled around a common axis, with specific base pairing (A-T, G-C) holding the strands together.

Explanation:
Biofertilizers contain living microorganisms like bacteria, cyanobacteria, and fungi that increase nutrient availability (e.g., nitrogen fixation, phosphorus solubilization) for plants. They are eco-friendly and sustainable. Chemical fertilizers are synthetic inorganic salts. Biopesticides control pests. Examples: Rhizobium, Azotobacter, mycorrhiza. Biofertilizers improve soil health without chemical residue.

Explanation:
Innate (natural) immunity is the non-specific defense mechanism present from birth, including physical barriers like skin and chemical barriers like stomach acid. Acquired (adaptive) immunity is highly specific and develops after the body is exposed to a specific pathogen or antigen, involving the production of antibodies and memory cells. Vaccines provide artificial immunity (specifically, artificial active immunity), not natural immunity, which is acquired through actual infection or from mother to child. Thus, statements 1 and 2 are correct.