| 1. | Oxygen obtained from liquefied air is usually about 99.5% pure .
由液化空气所取得的氧其纯度通常约为99.5%。 |
| 2. | The incubation period is short , usually around 1 - 3 days
潜伏期短，通常约一至三日。 |
| 3. | The incubation period is short , usually around 1 - 3 days
潜伏期短，通常约一至三日。 |
| 4. | The patient usually recovers in about two to four weeks
患者通常约于二至四星期内痊愈。 |
| 5. | The incubation period for influenza is usually about 1 - 3 days
流感的潜伏期通常约为一至三日。 |
| 6. | Oxygen obtained from liquefied air is usually about 99 . 5 % pure
由液化空气所取得的氧其纯度通常约为99 . 5 % 。 |
| 7. | About two to three weeks
潜伏期通常约二至三个星期。 |
| 8. | Normally around 10 seconds
通常约10秒 |
| 9. | The incubation period is usually around four weeks but may range from 15 days to 50 days
潜伏期通常约为4星期，但亦可能为期15至50日不等。 |
