The sky is clear, but the track can become covered with snow in a blink of an eye.

天空很清澈，但仅仅在一顷刻间里车痕就能被风雪覆盖。

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Evolution chose the Fibonacci pattern to help trees track the sun moving in the sky and to collect the most sunlight even in the thickest forest.

生物进化选择了斐波那契布局帮助树木跟踪在天空中不断移动的太阳，让树木即使在最茂盛的森林中也能尽量多地收集阳光。

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Suddenly ya boy's shrill voice rose into the sky. He traversed the dark unseen, leaving the track of his song across the hush of the evening.

天空里突然升起了一个男孩子的尖锐的歌声。他穿过看不见的黑暗，留下他的歌声的辙痕跨过黄昏的静谧。

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Pendleton also competes in three events, riding in the two-woman, two-lap team sprint alongside BMX ace Reade for Sky Track Cycling against Britain's Becky James and Jess Varnish.

BBC: Injury rules Rebecca Romero out of Manchester

Hoy opens his campaign on Friday in the men's sprint and will ride in all three sprint events - individual sprint, team sprint and Keirin - for Sky Track Cycling.

BBC: Injury rules Rebecca Romero out of Manchester

Campaigners say that one track south of Sky Hill has a strip of damage as wide as a four-lane motorway.

BBC: Motorbikes 'obliterating' tracks says environmentalist