Foods and fluids are mixed in the stomach by its muscular contractions.通過(guò)胃部肌肉的收縮食物和流質(zhì)在胃中混合。Contractions are much more common in speech than in writing.縮略詞在口語(yǔ)里比在書(shū)寫(xiě)中常見(jiàn)得多.Muscle contractions are powered by the chemical aden...