insert one dash where needed. mount rainiers liberty ridge climbing route is known for its amazing views and…

insert one dash where needed. mount rainiers liberty ridge climbing route is known for its amazing views and technical difficulty not to mention its long history of mountaineering accidents.

insert one dash where needed. mount rainiers liberty ridge climbing route is known for its amazing views and technical difficulty not to mention its long history of mountaineering accidents.

Answer

Brief Explanations:

The phrase "not to mention its long history of mountaineering accidents" is an added - on thought. A dash can be used to set it off from the main clause.

Answer:

Mount Rainier's Liberty Ridge climbing route is known for its amazing views and technical difficulty — not to mention its long history of mountaineering accidents.