Please translate the following poetry: 你是一树一树的花开，是燕/在梁间呢喃，--你是爱，是暖/是诗的一篇，你是人间的四月天。
You are blooming buds of trees, or a swift swallow/whispering at my window, you are love, and mellow./a chapter of poetry, and tender april of mondialito.
What is Revelation Principle in Game Theory? Please write down the intuition.
Revelation Principle states that, if the allocation y*(.) can be implemented through some mechanism, then it can also be implemented through a direct truthful mechanism where the Agent reveals his information.
How to find out whether a time series variable possesses a unit root or not? Please be as specific as possible.
The most common ways are DF test(Dickey–Fuller test) and ADF(augmented Dickey–Fuller test) test. DF test does not require lags. However, for ADF test, we should first decide how many lags to add. Basic ways are SIC(BIC), AIC, or general-to-specific. After choosing the optimal lag, we could conduct ADF test and to see if it has a unit root or not.