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 aUturn in its course to flow into India. ThisUturn is due to

• A. Uplift of folded Himalayan series
• B. Syntaxial bending of geologically young Himalayas
• C. Geo-tectonic disturbance in the tertiary folded mountain chains
• D. Both (a) and (b) above