______ WAS ONE OF THE MOST DIFFICULT TASKS PIONEERS FACED ON THEIR...

20. - 25 DE THI HOC KI 1 MON TIENG ANH LOP 12 CO DAP AN
25 DE THI HOC KI 1 MON TIENG ANH LOP 12 CO DAP AN

20.

______ was one of the most difficult tasks pioneers faced on their journeys west.

A. Crossing rivers

B. While crossing rivers C. Rivers being crossed D. By crossing rivers