My mother underwent major surgery last year. 我母親去年動(dòng)過(guò)大手術(shù)。
No major environmental pollution accident has occurred in Tibet, and most of its major rivers and lakes are in a primordial state. 全區沒(méi)有發(fā)生過(guò)大的環(huán)境污染事故,主要江河湖泊大多仍處于原生狀態(tài)。