The normal life span of human red blood cells is about: MCQ with Answer and Explanation

Explanation:
Self-pollination (autogamy) occurs within the same flower or between flowers of the same plant. Cross-pollination (allogamy) involves different plants. Hydrophily is pollination by water, anemophily by wind. Self-pollination ensures genetic uniformity, while cross-pollination promotes variation. Cleistogamous flowers (e.g., groundnut) are obligate self-pollinators.

Explanation:
Double circulation (pulmonary and systemic) with a four-chambered heart keeps oxygenated and deoxygenated blood separate, increasing efficiency. R correctly explains A.

Explanation:
Bt cotton contains cry genes from Bacillus thuringiensis, producing insecticidal proteins toxic to bollworms, reducing pesticide use.