The correct answer is option 4 - K2.
Option 1 - Nanga Parbat is the ninth highest mountain peak in the world, located in Pakistan`s Gilgit-Baltistan region.
Option 2 - Nanda Devi is the second highest mountain peak in India and the 23rd highest peak in the world.
Option 3 - Kanchenjunga is the third highest mountain peak in the world, located in Nepal and Sikkim.
Option 4 - K2, also known as Mount Godwin-Austen or Chhogori, is the second highest mountain peak in the world after Mount Everest. It is located on the China-Pakistan border in the Karakoram range.
Therefore, the highest mountain peak among the given options is K2, making option 4 the correct answer.