In a dihybrid cross between two heterozygous pea plants (RrYy x RrYy), if the two genes are completely linked, the phenotypic ratio in the F2 generation will be: MCQ with Answer and Explanation

Explanation:
2,4-D is a synthetic auxin widely used as a selective herbicide. It kills broadleaf dicot weeds without harming monocot crops like wheat, rice, and lawn grasses, as dicots are more sensitive to auxin overdoses, which cause uncontrolled growth and eventual death. NAA and gibberellic acid are used for rooting and growth promotion, and kinetin is a cytokinin.

Explanation:
Thyroxine is an animal hormone secreted by the thyroid gland, regulating metabolism. Auxin, gibberellin, cytokinin, abscisic acid, and ethylene are plant hormones (phytohormones). Plant hormones control growth, development, and responses to environment. Thyroxine contains iodine and affects basal metabolic rate. Thus, thyroxine is unrelated to plant physiology.

Explanation:
Innate immunity is the non-specific defense mechanism present by birth, including physical barriers and phagocytes. Vaccination introduces antigens to stimulate the body's own antibody production, conferring artificial active immunity. Antibodies (immunoglobulins) are produced and secreted by B-lymphocytes (plasma cells), not T-lymphocytes, which are involved in cell-mediated immunity. Thus, statements 1 and 2 are correct.