The key doesn't fit the lock.

这把钥匙打不开这把锁。

《牛津词典》

The key thing with any shoe, high or flat, is that it should fit properly, not pinch your toes and have a degree of flexibility.

任何高跟或平底鞋的关键是要合脚，不要夹着脚趾，要有一定的灵活性。

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He and many others agree that maintaining a fit lifestyle is the key to keeping your brain healthy. That means eating right, exercising regularly and remaining socially active.

他和其它一些人都认为保持健康的生活方式是大脑健康的关键，也就是说应该注意饮食，经常锻炼身体和参加社会活动。

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Staying fit is key to living with AIDS, she says.

CNN: The girl who changed Magic Johnson

Optional radio censorship isn't the only new feature for MyKey, which allows owners to program a key to fit their specific level of paranoia -- the new version allows parents to set top speeds between 65 and 80mph, instead of the previous fixed cap of 80mph.

ENGADGET: Ford MyKey adds radio censorship to further control teen driving habits

The challenge of rebuilding the Cubs would be a good fit for the low-key Girardi.

FORBES: Girardi Likely To Manage Cubs In 2011