The correct answer is option B, Shipki La.

The Satluj River is one of the major rivers in northern India and is an important tributary of the Indus River. It originates from the Mansarovar Lake in Tibet and flows through the western Himalayas before entering India.

Here is a detailed explanation of why the Satluj River enters India through the Shipki La pass:

1. Location of Shipki La:
- The Shipki La pass is located in the Kinnaur district of Himachal Pradesh, India.
- It lies on the India-China border, specifically on the border between Himachal Pradesh in India and Tibet in China.

2. Satluj River's Origin:
- The Satluj River originates from the Rakshastal Lake near Mount Kailash in Tibet.
- It then flows southwest through Tibet before entering India.

3. Flow of Satluj River in Tibet:
- In Tibet, the Satluj River flows through the Ngari Prefecture and passes through the Shipki La pass.
- The Shipki La pass is situated at an altitude of around 4,500 meters (14,800 feet) above sea level.

4. India-China Border:
- The Shipki La pass serves as an important route between India and China.
- It is one of the few open border crossings between the two countries and is used for trade and commerce.

5. Satluj River's Entry into India:
- After flowing through the Shipki La pass, the Satluj River enters the Kinnaur district of Himachal Pradesh in India.
- It then continues its journey through the Indian Himalayas, passing through places like Rampur, Shimla, and Bilaspur before merging with the Beas River near Harike in Punjab.

In conclusion, the Satluj River enters India through the Shipki La pass, which is located in the Kinnaur district of Himachal Pradesh. This pass serves as an important entry point for the river from Tibet and also acts as a trade route between India and China.