嗯，一点五公顷的树木就能产生足够的氧气让你们全班的同学健康地活一年。
Well, one and a half hectares of trees could produce enough oxygen to keep your whole class alive and healthy for a whole year.
大约需要7到8棵树产生足够一个人呼吸一年的氧气。
It takes about 7 to 8 trees to make enough O2 for one person to breathe for a year.
走路时小腿肌肉需要更多氧气，但因为血液流动被限制，肌肉就无法获得足够的氧气，进而产生痉挛。
When walking the calf muscles need more oxygen, but because the blood flow is restricted the muscles cannot obtain enough oxygen from the blood and cramp occurs.
这样身体准备不够，就无法保证足够的氧气传输和抵消了快跑的副产品，这样就很难产生最够的能量以达到最终跑步的目的。Coster说。
The body is thus ill-prepared to adequately transport oxygen and offset the by-products of fast running, so it's harder to generate the power to run at goal pace, says Coster.
这样身体准备不够，就无法保证足够的氧气传输和抵消了快跑的副产品，这样就很难产生最够的能量以达到最终跑步的目的。Coster说。
The body is thus ill-prepared to adequately transport oxygen and offset the by-products of fast running, so it's harder to generate the power to run at goal pace, says Coster.
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