1. It is true during their explorations they often faced difficulties and dangers of the most perilous nature.
    确实在探险中, 他们经常面临着各种最有危险性的艰难和险阻.

2. It is true that during their explorations they often faced difficulties and dangers of the most perilous nature,
    确实，在探险中他们经常遇到惊心动魄的困难和危险，