他的情绪变化不定，一会儿恐惧一会儿生气。
这一计算由于变化不定的气候而更加困难。
Such calculations are made more difficult by the uncertainty surrounding climate change.
浏览器也往往会向标题中添加空格，使按钮的长度变化不定。
Browsers also often add padding Spaces to the captions, giving the buttons varying lengths.
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