The answer is D.

The sentence discusses the characteristics of the Himalayas, emphasizing their jagged peaks and steep drops, which indicate their relative youth. The blank should be filled with a word that matches the context of sharp or steep declines, as contrasted with older, more eroded mountains that are smaller and rounder.

Blank (i):
A. overweening: Overweening means excessively proud or arrogant, which does not describe a physical feature of mountains.
B. notorious: Notorious means famous for something negative. While it could be applied to the mountains in a metaphorical sense, it doesn't fit the literal description of their features.
C. surreptitious: Surreptitious means secret or stealthy, which is unrelated to describing a mountain's physical characteristics.
D. precipitous: Precipitous means extremely steep or sudden, which perfectly matches the context of describing the steep drops of the Himalayas.
E. nascent: Nascent means just coming into existence or developing, which doesn’t fit well with the idea of physical mountain features.