探险队在攀登珠穆朗玛峰前，在海拔4000米处搭建了大本营。

The expedition team set up their ___base-camp at 4,000 meters before climbing Mount Everest.

登山队在海拔5000米处建立了大本营，为登顶做准备。

The climbing team set up their ___base-camp at 5,000 meters to prepare for the summit attempt.

他们在山区建立了前线作战的临时基地。

They set up a ___base-camp in the mountains for frontline operations.