The intrepid mountaineers who scaled the peak in winter should be specially congratulated.

Answer: Option A

Bold : (of a person, action, or idea) showing a willingness to take risks; confident and courageous.
Timid : showing a lack of courage or confidence; easily frightened.
Unadventurous : not offering, involving, or eager for new or stimulating things.
Unimaginative : not readily using or demonstrating the use of the imagination; stolid and somewhat dull.
Intrepid : fearless; adventurous (often used for rhetorical or humorous effect).

Synonym of Intrepid is Bold