Let's analyze each statement for its accuracy:
1. The Assam Himalayas are lower in elevation compared to the Nepal Himalayas.
- This statement is correct. The Nepal Himalayas are known for having the tallest peaks like Mount Everest and Kanchenjunga, making them significantly higher in elevation compared to the Assam Himalayas.
2. The Western Syntaxial Bend occurs near Namcha Barwa in Arunachal Pradesh.
- This statement is incorrect. The Western Syntaxial Bend actually occurs near Nanga Parbat where the Indus River cuts a deep gorge, not near Namcha Barwa. Namcha Barwa is associated with the Eastern Syntaxial Bend.
3. The Eastern Syntaxial Bend marks the eastern extremity of the Himalayas.
- This statement is correct. The Eastern Syntaxial Bend occurs near Namcha Barwa in Arunachal Pradesh and marks the eastern extremity of the Himalayas.
Therefore, the correct statements are 1 and 3. Hence, the correct answer is Option C.