The answer is 'colluded', because it means that they schemed to do it secretly. The other options aren't possible here, and most of them are adjectives, and you need a verb.
<u><em>A sachem is the chief or leader of a tribe, and having anyone of your community do an act of defection (change loyalty to the opposite side) is the beginning of lots of issues, those including: treason, increasing number of deserters, a weakening tribe, etc. Those are the reasons why a sachem should be concern about defection.</em></u>
Definitely Whispered, because he quietly leaned over<span />
Muir's writing is on both the beauty and harshness of nature. He talks about the beauty of the flower he discovered, but then talks about having to go without supper or blankets and how storms and the harsh weather conditions became welcomed after probably showing up a lot.