高海拔地区种树是世界级难题。阿里地区的技术人员经过反复论证，确定了毛头柳、青海杨等二十多种适宜高海拔种植的苗木，并采取了给树木注营养液、裹黑纱棉等八大防护措施保证成活率，为藏西高原增添一抹绿色。生命禁区能够出现绿色证明了
We have a washing machine to do that sort of thing. A. needn’t have washed B. shouldn’t have washed C. must not have washed D. can not have washed 19/25 2.They have ___ baby. A. a five month old B. a fifth-month-old C. a five-month-old D. a five-months-old 3....