The Brahmaputra, Indus, Ayeyarwady and Mekong rivers originate in Tibet and flow through narrow and parallel mountain ranges in their upper courses. Of these, the first two rivers make 'U' turn while crossing the Himalayas and flow into India. This 'U' turn is due to

• A. Uplift of folded Himalayan series out of Tethys Sea.
• B. Syntaxial bending of geologically young Himalayas
• C. Geo-tectonic disturbances in the tertiary folded mountain chain.
• D. Both [a] and [b] above