If you don't want to fail the final exam,your best bet is to work on your study really hard.
【解释】这里先来解释下bet，bet的意思是赌博、赌钱、下注，我们用得比较多的短语You bet，算是美国人的口头禅，表示毋庸置疑，肯定的。

那么best bet最好的赌注，有什么深层次的含义呢？

someone's best bet used to tell sb what is the best
action for them to take to get the result they want.
best bet本来是赛马术语，后来引申为以最好的方式达到他们所想要得到的结果。
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【翻译】今天的句子If you don't want to fail the final exam,your best bet is to work on your study really hard.可以翻译为——如果你不想期末考试不及格，你现在最好的选择是真正努力的在学习上下工夫。
【应用】两则例句送给你
1
If you want a cheap jacket, your best bet is to try the second-hand shops.你如果要买便宜点的夹克，最好去二手商店看看。
2
I told him his best bet would be to get a bus as there are no direct trains. 我跟他说过他最好坐汽车去，因为这里没有直达的火车。