Photo taken on May 9, 2020 shows the advance camp at an altitude of 6,500 meters on Mount Qomolangma. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food. (Photos: Xinhua)

A climber has food at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

Chefs prepare food at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

A chef cooks at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

A chef cooks at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

A chef prepares food at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

Photo taken on May 10, 2020 shows a kitchen at the advance camp at an altitude of 6,500 meters on Mount Qomolangma. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

A chef stir-frys a dish at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

Chefs prepare food at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.

Chefs prepare food at the advance camp at an altitude of 6,500 meters on Mount Qomolangma, May 10, 2020. To cope with the high altitude and low pressure at the advance camp, chefs use pressure cookers to prepare food.