Here, the first string is defined with a pair of single quotes. The second one USES a pair of double quotes.

这里，第一个字符串使用一对单引号定义，第二个字符串使用一对双引号定义。

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Step 2: To perform a single step of an evaluation, W3Eval finds the operator with the highest priority inside the deepest nested pair of parentheses.

步骤 2：要实现求值的单步执行，W3Eval 在嵌套最深的那对括号中找出优先级最高的操作符。

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You may have only 15, and you use every single pair instead of thinking: Why the heck do I have 3 pairs of the same shoe in different colours?

反之，你可能只有 15 双鞋，而你在穿每一双鞋的时候再也不用去想， 搞什么鬼，为什么我会有三双颜色不同样式相同的鞋？

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Camera in hand, we shadowed them across baggage claim, taking half a dozen blurry pictures of the pair before snapping a single semi-decent image, in which Rekers was captured preparing to push a cumbersome luggage cart into an elevator.

CNN: Reporters find tragic story amid embarrassing scandal

The single solution on a card joins tap-to-pair functionality and ease-of-use of NFC with speed, coverage and performance benefits of 5G WiFi to create the ideal platform for highly-mobile devices.

ENGADGET: Broadcom intros quad-combo, fast single-card wireless chipsets that put NFC at center stage

While a single, bed-width cushion creates an orderly line, a pair of bolsters one for each half of the bed makes more sense for bedmates with opposing propping needs.

WSJ: Bolster Cushions Win Best Supporting Rolls