a 0.3 per cent contraction in output产量缩减了0.3%

From her first contractions to the birth of the baby took only three hours.从她第一次宫缩到孩子出生只用了三个小时。

the contraction and expansion of blood vessels血管的收缩和扩张

Foods and fluids are mixed in the stomach by its muscular contractions.胃里的食物和液体通过肌肉收缩混合在一起。

'It's' (with an apostrophe) should be used only as a contraction for 'it is'.It's(带撇号)只能用作it is的缩写。