One optimistic estimate is that half the world's people might speak English by 2050.
一个乐观的估计是到2050年世界上大概有一半的人会说英语。
He said by an optimistic estimate, it would take between 10 and 20 years for the reef to recover.
他说，根据乐观的估计，大堡礁将需要10年到20年来恢复。
He said by an optimistic estimate, it would take between 10 and 20 years for the reef to recover.
他说，根据乐观的估计，大堡礁将需要10年到20年来恢复。
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