Even though many soldiers from other branches of the military or even allied forces can get the opportunity to attend Ranger school and obtain a Ranger tab during graduation; I believe that it is only open to the Ranger qualified soldiers in the Army as each unit only has a certain amount of slots available for the competition. Most of these units already have plenty of candidates to pick the best duo from; In comparison to another branch that might just have a few service members to choose from. Hope this helps.
This is the second event. They just finished running 7 miles and at the halfway point, they swam across a lake and picked up a sandbag to carry to this point.