In picture "A" above you can see with the wrist bent back that part of the weight of the ball will be resting on the base of the thumb.

在图片“A”你能看手腕向后摆动时，一部分的球的重量会移向拇指的下部。

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So Tom unwound the thread from one of his needles, and each boy pricked the ball of his thumb and squeezed out a drop of blood.

31于是汤姆拿出一根针，去掉了线。两个孩子各自往大拇指上戳了一下，然后挤出两滴血来。

youdao

So Tom unwound the thread from one of his needles, and each boy pricked the ball of his thumb and squeezed out a drop of blood.

31于是汤姆拿出一根针，去掉了线。两个孩子各自往大拇指上戳了一下，然后挤出两滴血来。

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