Levine acknowledges that implementing an environment that encourages performative ties isn "t necessarily easy."

拉文承认，营建一个鼓励主动性联系的环境并不一定非常容易。

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It isn't the case that defending easy dominates defending hard.

防守平坦之途并非优于防守崎岖之途

耶鲁公开课 - 博弈论课程节选

"It is a game that isn't easy to analyse, " said Nadal.

BBC: Nadal crashes to defeat in Madrid

As a parent of three young children, I can imagine that this isn't easy to do.

CNN: Mick Jagger's lesson on parenting

That isn't an easy realization to come to, and for the past few years, Teixeira has fought it hard.

WSJ: Teixeira Knows His Limits