The correct answer is (a) Kalindi.
The Kalindi Pass is a high mountain pass in the Garhwal Himalayas in the Indian state of Uttarakhand. It connects the Darma Valley in the north with the Byas Valley in the south. The pass is located at an elevation of 4,800 meters (15,750 feet) and is a popular trekking destination.
The Kalindi Pass is one of the most difficult passes in the Garhwal Himalayas. It is a long and arduous trek, and the pass is often covered in snow and ice. The best time to trek to the Kalindi Pass is from June to September.
The Kalindi Pass is a beautiful and remote place. The views from the pass are stunning, and the trek is a great way to experience the natural beauty of the Garhwal Himalayas.
The other options are incorrect because they do not connect the Darma and Byas valleys.
(b) Sinala Pass connects the Darma Valley with the Pin Parvati Valley.
(c) Laspa Pass connects the Darma Valley with the Spiti Valley.
(d) Khanj Pass connects the Darma Valley with the Kinnaur Valley.