The Brahmaputra, Irrawady and Mekong rivers originate in Tibet and flow through narrow and parallel mountain ranges in their upper reaches: Of these rivers, Brahmaputra makes a "U" turn in its course to flow into India. This "U" turn is due to

• A. plift of folded Himalayan series
• B. yntaxial bending of geologically young Himalayas
• C. eo-tectonic disturbance in the tertiary folded mountain chains
• D. oth (a) and (b) above