Longer life spans are one reason, along with an increasingly uncertain financial picture.
拥有更长的寿命是一个原因，与越来越不确定的金融前景也有关系。
The reason for this is still uncertain, but it is obviously related to spatial ability.
其中的原因还不明朗，但这显然和空间感有关。
The physical reason for this outburst is still uncertain.
然而，产生这次爆发的物理原因尚不清楚。
The physical reason for this outburst is still uncertain.
然而，产生这次爆发的物理原因尚不清楚。
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