China's experts began to study the design of the torch two years ago in order to keep the flame alight in the oxygen-thin air.

登山队员用一根棍子将火焰移取到火炬上。中国专家两年前就开始研究火炬设计图，为了使火炬能在氧气稀薄的地方燃烧。

youdao

Mountain climbers often carry oxygen tanks because the air is very thin at high altitudes.

登山者通常会携带氧气筒，因为在极高的地带空气相当稀薄。

youdao

Thee air seemed thin as though its combination of gases had little oxygen left.

空气似乎很稀薄，好像在混合的气体中剩下的氧气很少。 。

youdao

At about nineteen-thousand meters, the air is so thin and the amount of oxygen so small that a person needs a lot of special equipment to survive.

VOA: special.2011.04.06